Visible Broadband Imager Red Channel Critical Design Definition · 2020. 1. 22. · The F/20.3 focal plane is tilted 4.29˚ (due to the tilted field provided by the ATST) and is fixed

Project Documentation Document SPEC-0126

Rev A

Advanced Technology Solar Telescope 950 N. Cherry Avenue Tucson, AZ 85719

Phone 520-318-8102 [email protected] http://atst.nso.edu Fax 520-318-8500

Visible Broadband Imager

Red Channel

Critical Design Definition

William McBride, Scott Gregory, Andrew Ferayorni, Friedrich Wöger

VBI Instrument Group

September 12, 2012

VBI-R Critical Design Definition

SPEC-0126, Rev A Page ii

REVISION SUMMARY:

1. Date: June 4, 2012 Revision: Initial version Changes: Draft

2. Date: Sept 12, 2012 Revision: Rev A Changes: Ready for VBI Red CDR. Initial formal document.


SPEC-0126, Rev A Page iii

Table of Contents

1. INTRODUCTION ...................................................................................................... 5

2. OPTICAL DESIGN .................................................................................................... 6

2.1 VBI RED DESIGN REQUIREMENTS ..................................................................... 7

2.2 INTERFACE TO VBI RED ....................................................................................... 7

2.2.1 Image Quality ................................................................................................................. 8

2.2.2 Angle of Incidence .......................................................................................................... 9

2.2.3 Pupil Footprints on Filters ............................................................................................... 9

2.2.4 Grid Distortion ...............................................................................................................10

2.3 OPTICAL TOLERANCE ANALYSIS AND ERROR BUDGET ................................. 11

2.3.1 The Zemax Tolerance Model .........................................................................................11

2.3.2 Monte Carlo Results ......................................................................................................15

2.3.3 Conclusions ...................................................................................................................17

2.4 OPTICAL ALIGNMENT ......................................................................................... 17

2.5 SPURIOUS LIGHT MITIGATION PLAN .......................................................................... 18

3. HARDWARE DESIGN ............................................................................................ 19

3.1 FOLD MIRROR #1 MOUNT .......................................................................................... 22

3.2 FILTER WHEEL ......................................................................................................... 22

4. SOFTWARE DESIGN ............................................................................................. 25

4.1 VBI RED CONTROL SYSTEM SOFTWARE ................................................................... 25

4.2 SYNCHRONIZATION OF VBI BLUE AND VBI RED ......................................................... 25

4.2.1 Alignment of Observation Steps ....................................................................................25

4.2.2 Establishing Initial Start Time for Cameras ....................................................................30

5. TEST PLAN ............................................................................................................ 33

5.1 INTERFERENCE FILTER TESTING ............................................................................... 33

5.2 INSTRUMENT TEST PLAN .......................................................................................... 34

5.2.1 Alpha Phase ..................................................................................................................34

5.2.2 Beta Phase....................................................................................................................34

5.2.3 Lab Phase .....................................................................................................................35

5.2.4 Engineering Phase ........................................................................................................35

5.2.5 Speckle Phase ..............................................................................................................35

5.2.6 Periodic Integration Phases. ..........................................................................................35

5.2.7 Shipping Phase .............................................................................................................35


SPEC-0126, Rev A Page iv

5.2.8 IT&C Phase ...................................................................................................................36

5.2.9 Science Verification .......................................................................................................36

6. BUDGET ................................................................................................................. 37

6.1 LABOR .................................................................................................................... 37

6.2 FILTERS ................................................................................................................. 37

6.3 OPTICS .................................................................................................................. 38

6.4 CONTROLS & MECHANICAL ...................................................................................... 38

6.5 DATA HANDLING SYSTEM AND SPECKLE IMAGE RECONSTRUCTION ............................. 38

6.6 BILL OF MATERIALS ................................................................................................. 39

7. SCHEDULE ............................................................................................................ 42

8. HAZARD ANALYSIS .............................................................................................. 43

9. PROJECT MANAGEMENT .................................................................................... 44

10. RISK ASSESSMENT ............................................................................................ 45

10.1 VBI RISK REGISTER .............................................................................................. 45


SPEC-0126, Rev A Page 5 of 45

1. INTRODUCTION

The Visible Broadband Imager (VBI) is a first-light high spatial resolution imaging instrument for the

Advanced Technology Solar Telescope (ATST). For many reasons related to science, mechanics, optics

and management, there are two separate VBI channels, the "blue" channel and the "red" channel, each

capable of imaging four discrete wavelengths and operated either simultaneously or independently.

The VBI red design is closely related to that of the VBI blue channel described in SPEC-0107, the VBI

Critical Design Document (CDD). In this document, the VBI red CDD, modifications and additions to

the VBI blue design are recorded that are mainly needed to address the VBI red's optical and mechanical

requirements, as well as the synchronization requirements of the VBI red and blue channel.

For a more detailed description of the VBI and items that are common to both channels, refer to SPEC-

0107.



2. OPTICAL DESIGN

Figure 1 VBI Red Optical Design

The primary driver for the VBI optical design choice was to keep the instrument as simple as possible

consistent with achieving the science requirements. The decisions that led to the VBI optical designs are

documented in SPEC-0107 the VBI blue channel CDD. The red design is very similar to the blue design;

like the blue channel, the red channel is a four lens design which includes two doublet and two singlet

lenses. The main difference in the design is in the folding of the optics necessitated by the location and

orientation of the red channel in the Coudé Lab (see Figure 2).

Figure 1 shows the four lens design. The collimator lens is used to compensate the axial chromatic

aberration for various filters and travels a total of 21mm between the longest and shortest wavelengths.

The F/20.3 focal plane is tilted 4.29˚ (due to the tilted field provided by the ATST) and is fixed for all

wavelengths. Focusing is accomplished by translating the collimator lens along the optical axis.

The objective lens forms an F/13 focal-plane ~ 2600 mm downstream. The doublet is comprised of S-

TIL6 and BK7 glass and has one conic surface. The silica field lens works with the collimator to form a

65 mm diameter pupil at the location of the filter. The collimator is another silica singlet whose main

function is to collimate the F/13 focal plane. The image doublet is very similar in composition to the relay

doublet and images the F/20.3 focal plane at the camera detector.



2.1 VBI RED DESIGN REQUIREMENTS

The following were the requirements for the VBI red channel optical design:

FOV: ≈ 2.8 arcmin (round)

Performance: Diffraction limited over the FOV

F#: 20.3 at the detector plane

Wavelength range: 600 to 860 nm

Optimized wavelength: 656.3 nm

Chromatic focal shift: less than 100 mm at the detector between 600 - 860 nm

Filter acceptance angle: ≤ 1.4 degrees

Filter effective refractive index: ≥ 1.9

The filter must be located near a pupil within a collimated field.

Filter clear aperture: 65 mm

2.2 INTERFACE TO VBI RED

The optical interface to VBI is the facility beamsplitter shown in the red circle below. This interface is

described in detail in the Coudé Station to VBI Interface Control Document (ICD 3.1.3 to 3.2). The VBI

blue WBS number is 3.2.1 and the VBI red WBS number is 3.2.2.



Figure 2: VBI Red-ATST Optical Interface

2.2.1 Image Quality

Figure 3: Image Quality represented by Spot Diagrams. Left: Spot Diagram for 600 nm. Right: Spot Diagram for 860 nm



2.2.2 Angle of Incidence

The field angles produce the center ray tilt and the collimate errors produce the collimate ray tilts. In this

design the mean value of the central ray tilt is 1.71° (Figure 4).

Figure 4: Results for Filter AOI

2.2.3 Pupil Footprints on Filters

Figure 5: Pupil Footprints on all Filters (all wavelengths). Filter CA is 65mm, Filter Diameter is 70 mm.



2.2.4 Grid Distortion

The maximum grid distortion is always below 0.197% for all wavelengths (Figure 6).

Figure 6: Distortion Grid for 656.3 nm.



2.3 OPTICAL TOLERANCE ANALYSIS AND ERROR BUDGET

ASE Optics performed the optical tolerance analysis. The system performance specification is a peak-to-

valley wavefront error of less than 0.50 waves at 633 nm for all field positions. A Monte Carlo analysis

was performed to evaluate the probability that the specification can be met given the lens element

tolerances used.

All the tolerances from the previous VBI-Blue analysis have been carried over. The same homogeneity

models that were used for the non-silica elements have been carried over. The narrowband filter

wavefront model was updated to reflect the transmitted wavefront specification on the red channel filters.

New models were added for the interface error and the transmitted wavefront error of the three

beamsplitters.

A 1000 trial Monte Carlo analysis was performed as was done with the VBI-Blue analysis. This time the

same Zemax model was used to generate the sensitivities and run the Monte Carlo analysis. The pupil

filter was allowed to tip and tilt to minimize AOI and the merit function used in tolerancing weighted the

filter AOI. System effective focal length was allowed to vary, but remained between 79.47 and 79.82

meters for all Monte Carlo trials. The field lens location was fixed at 20 mm ahead of the intermediate

focus for all Monte Carlo trials. The most critical tolerance found was the filter wavefront error.

2.3.1 The Zemax Tolerance Model

The table below is the Zemax model used in the Monte Carlo analysis performed by ASE Optics. The

table shows the defined nominal, min, and max ranges of the compensators and tolerances. It uses just the

key tolerances that individually cause more than about 0.005 increase in RMS WFE. The table is used to

generate the Monte Carlo analysis shown in Figure 7.

# Type Int1 Int2 Int3 Nominal Min Max Comment

1 TOFF - - - - - -

** Element spacing

compensators:

2 COMP 74 0 - 2109.414 -300 300 L1 focus

3 COMP 81 0 - -616.088 -200 200 Collimator focus

4 COMP 99 0 - 0 -200 200 Image lens focus

5 TOFF - - - - - -

** Filter tilt

compensator:

6 CPAR 87 3 - -1.31E-03 -5 5 x position

7 CPAR 87 4 - 2.02E-03 -5 5 y position

8 TOFF - - - - - -

** Image lens x-y

position compensator:

9 CPAR 92 1 - 0.073 -5 5 x position

10 CPAR 92 2 - 0.255 -5 5 y position

11 TOFF - - - - - -

** Focal plane tilt

compensator:

12 CPAR 99 3 - -4.435 -3 3 x rotation

13 CPAR 99 4 - 0.042 -3 3 y rotation

14 TOFF - - - - - -

** Focus

compensators:

15 CMCO 5 1 - 4.597 -10 10 Config 1 focus

16 CMCO 5 3 - -16.584 -10 10 Config 3 focus



17 TOFF - - - - - -

18 TWAV - - - - 0.633 -

Default test

wavelength.

19 TOFF - - - - - - ** Interface error:

20 TEZI 49 9 5 0 -2.08E-05 2.08E-05

21 SAVE 1 - - - - -

22 TOFF - - - - - -

** Beamsplitter

wavefront model:

23 TEZI 52 37 5 0 -4.20E-07 4.20E-07 BS1

24 TEZI 57 37 5 0 -1.04E-06 1.04E-06 BS2

25 TEZI 65 37 5 0 -1.04E-06 1.04E-06 BS3

26 TOFF - - - - - -

** Pupil filter

wavefront model:

27 TEZI 88 9 5 0 -7.56E-05 7.56E-05

28 SAVE 2 - - - - -

29 TOFF - - - - - -

** Glass homogeneity

tolerances:

30 TEZI 69 37 10 0 -1.69E-05 1.69E-05 L1 LLF1 grade H3

31 TEZI 71 37 10 0 -2.97E-05 2.97E-05 L1 BK7 grade H3

32 TEZI 93 37 10 0 -1.04E-05 1.04E-05 L4 PSK3 grade H3

33 TEZI 96 37 10 0 -7.68E-06 7.68E-06 L4 LLF1 grade H3

34 TOFF - - - - - -

** Tolerances on

surface radii:

35 TRAD 69 - - -2132.8 -22 22 L1 - objective

36 TRAD 70 - - -752.6 -8 8

37 TRAD 71 - - 3692 -40 40

38 TRAD 76 - - 371 -4 4 L2 - field lens

39 TRAD 77 - - 1070 -20 20

40 TRAD 83 - - -1265 -20 20 L3 - collimate lens

41 TRAD 84 - - 651.7 -10 10

42 TRAD 93 - - -276.6 -3 3 L4 - image lens

43 TRAD 94 - - 276.6 -3 3

44 TRAD 95 - - 276.6 -3 3

45 TRAD 96 - - -439.3 -5 5

46 TOFF - - - - - -

** Tolerance on conic

constants:

47 TCON 71 - - -16.657 -0.2 0.2 L1 - objective

48 TCON 84 - - -2.727 -0.1 0.1 L3 - Collimate lens

49 TOFF - - - - - -

** Element thickness

tolerances:

50 TTHI 69 69 - -30 -0.5 0.5 L1

51 TTHI 70 70 - -40 -0.5 0.5

52 TTHI 76 76 - 6 -0.2 0.2 L2

53 TTHI 83 83 - -10 -0.2 0.2 L3

54 TTHI 93 93 - -9 -0.2 0.2 L4



55 TTHI 95 95 - -7 -0.2 0.2

56 TOFF - - - - - -

** Index of refraction

tolerances:

57 TIND 69 - - 1.548 -1.00E-03 1.00E-03 L1

58 TIND 70 - - 1.517 -1.00E-03 1.00E-03

59 TIND 76 - - 1.458 -1.00E-03 1.00E-03 L2

60 TIND 83 - - 1.458 -1.00E-03 1.00E-03 L3

61 TIND 93 - - 1.603 -7.00E-04 7.00E-04 L4

62 TIND 95 - - 1.62 -7.00E-04 7.00E-04

63 TOFF - - - - - -

** Abbe number

tolerances:

64 TABB 69 - - 45.75 -0.458 0.458

65 TABB 70 - - 64.167 -0.642 0.642

66 TABB 76 - - 67.821 -0.678 0.678

67 TABB 83 - - 67.821 -0.678 0.678

68 TABB 93 - - 60.597 -0.606 0.606

69 TABB 95 - - 36.431 -0.364 0.364

70 TOFF - - - - - -

Element tilt/decenter

tolerances:

71 TEDX 69 71 - 0 -2 2 L1

72 TEDY 69 71 - 0 -2 2

73 TETX 69 71 - 0 -0.1 0.1

74 TETY 69 71 - 0 -0.1 0.1

75 TEDX 76 77 - 0 -2 2 L2

76 TEDY 76 77 - 0 -2 2

77 TETX 76 77 - 0 -0.2 0.2

78 TETY 76 77 - 0 -0.2 0.2

79 TEDX 83 84 - 0 -2 2 L3

80 TEDY 83 84 - 0 -2 2

81 TETX 83 84 - 0 -0.2 0.2

82 TETY 83 84 - 0 -0.2 0.2

83 TOFF - - - - - -

** Surface

tilt/decenter

tolerances:

84 TSTX 69 - - 0 -0.05 0.05 L1

85 TSTY 69 - - 0 -0.05 0.05

86 TSTX 70 - - 0 -0.05 0.05

87 TSTY 70 - - 0 -0.05 0.05

88 TSTX 71 - - 0 -0.05 0.05

89 TSTY 71 - - 0 -0.05 0.05

90 TSTX 76 - - 0 -0.1 0.1 L2 - Field lens

91 TSTY 76 - - 0 -0.1 0.1

92 TSTX 77 - - 0 -0.1 0.1

93 TSTY 77 - - 0 -0.1 0.1



94 TSTX 83 - - 0 -0.1 0.1 L3 - Collimate lens

95 TSTY 83 - - 0 -0.1 0.1

96 TSTX 84 - - 0 -0.1 0.1

97 TSTY 84 - - 0 -0.1 0.1

98 TSTX 93 - - 0 -0.1 0.1 L4 - Image lens

99 TSTY 93 - - 0 -0.1 0.1

100 TSTX 94 - - 0 -0.1 0.1

101 TSTY 94 - - 0 -0.1 0.1

102 TSTX 95 - - 0 -0.1 0.1

103 TSTY 95 - - 0 -0.1 0.1

104 TSTX 96 - - 0 -0.1 0.1

105 TSTY 96 - - 0 -0.1 0.1

106 TOFF - - - - - -

** Irregularity

tolerances:

107 TIRR 69 - - 0 -0.5 0.5 L1

108 TIRR 70 - - 0 -0.5 0.5

109 TIRR 71 - - 0 -0.5 0.5

110 TIRR 76 - - 0 -0.5 0.5 L2

111 TIRR 77 - - 0 -0.5 0.5

112 TIRR 83 - - 0 -0.25 0.25 L3

113 TIRR 84 - - 0 -0.25 0.25

114 TIRR 93 - - 0 -0.25 0.25 L4

115 TIRR 94 - - 0 -0.25 0.25

116 TIRR 95 - - 0 -0.25 0.25

117 TIRR 96 - - 0 -0.25 0.25

118 TOFF - - - - - -

** Fold mirror

irregularity tolerances:

119 TIRR 62 - - 0 -0.125 0.125 beamsplitter

120 TIRR 73 - - 0 -0.125 0.125 fold mirror 1

121 TIRR 80 - - 0 -0.125 0.125 fold mirror 2

Table 1: Zemax Model used in the Monte Carlo



2.3.2 Monte Carlo Results

The Monte Carlo result indicates the design will be less than ½ wave P-V at 656nm 91.6% of the time for

the full field 2.8 arcmin FOV. The results also indicate the design will be less than ½ wave P-V at 860nm

98.4% of the time with the full FOV.

Figure 7: Monte Carlo Results for full FOV.



Figure 8: Monte Carlo Results for 1.4 arcmin FOV



Figure 9: Compensator Ranges

2.3.3 Conclusions

A tolerance analysis of the VBI-R system has been performed. The results show the same primary

sensitivities as the VBI-B system. The filter wavefront dominates the other tolerances in producing the

system performance. The beamsplitter wavefront is not critical to the system performance at λ/20 and

could be relaxed to λ/10.

2.4 OPTICAL ALIGNMENT

By simplifying the optical design to an all-refractive design, we have significantly mitigated alignment

risk. In our reflective designs, the sensitivity of off-axis parabola alignment was far more severe.

The dichroic beamsplitter that transmits longer wavelengths to the VBI Red is the optical interface and

provided by the facility. It is the responsibility of the appropriate ATST staff to ensure that this interface

is properly aligned before starting the VBI Red alignment.

It is highly likely that the VBI Red objective and fold mirror will share an optical table with other facility

fore-optics. Thus, we expect this table to be properly aligned when installing the objective and fold

mirror. The remaining optics and detector will most likely reside on another optical bench.

The installation and alignment will begin with installing the objective the proper distance from the

dichroic beamsplitter. All lenses will have masks to define the center of the lens. With the mask installed,



we will use a GOS pinhole target with sunlight, at the Gregorian Optical Station (GOS) to center the lens

in the optical beam. We will adjust tilt by aligning the reflection from the lens with the beam on the fore-

optics. The large fold mirror will be installed next. The optical bench for the remaining optics and

detector will then be installed and aligned to a row of threaded holes on the bench using the GOS pinhole

target with sunlight. The remaining lenses will be installed and aligned using the same procedure.

This type of alignment procedure has been used successfully at the DST for many years. In addition, we

anticipate using the facility wavefront sensor, fiber interferometer, and the VBI detector to optimize the

focal plane optical performance.

2.5 SPURIOUS LIGHT MITIGATION PLAN

Spurious light reaching a detector is always a significant concern when designing and operating a

scientific instrument. Sources of spurious light typically come from the instrument itself, reflections from

other instruments, and the lab itself in which they operate.

Spurious light emitted within the instrument itself is typically introduced by front and back surface

reflections of optical elements such as lenses, windows, beam-splitters, and filters. To mitigate this issue,

we have minimized such reflections by optimizing the anti-reflection coatings over the wavelength range

of the instrument. The achievable result is < 1% reflection from 600 to 1100 nm; < 0.25% for VBI-B from

390-490 nm.

The VBI-Red will be setup and tested within a lab equipped with a solar light feed before shipping to the

ATST site. During this process, the team will identify and evaluate spurious light sources within the

instrument by darkening the lab and blocking light sources from the lab itself. This is typical of custom

observing setups at the Dunn Solar Telescope where the instrument is cloaked with darkroom cloth and

baffles are added to eliminate spurious emissions within the instrument. Having identified the sources and

mitigations, the team will design and construct fixed blockers and baffles to be affixed securely to the

optical table supporting the instrument. Having installed these elements in the lab, the team will

reevaluate the performance mitigation prior to shipping the instrument to the ATST.

The ATST will have a laminar down-flow of conditioned air in the coudé lab to mitigate local seeing and

dust accumulation. As such, instruments are not envisioned to require covers for the entire instrument.

Therefore, it is critical that the coudé lab itself will not generate sources of spurious emission into the

instruments. Should the lab generate such emissions, it is envisioned that these sources will be blocked

within the instrument with additional tubes and baffles developed in the IT&C phase.

It is difficult to predict spurious light sources from other instruments in the coudé lab. However, the

mitigation within the VBI-Red is expected to resemble the mitigation from stray light coming from the

coudé lab.



3. HARDWARE DESIGN

The VBI Red design is mechanically identical to the VBI Blue design described in SPEC-0107 with only

two differences. The first mirror of the VBI Red optical design has a small enough angle of incidence in

the reflected light beam to allow the use of an off the shelf mount that fits within the Coudé room

specified beam height of 250 mm. (In the Blue design the first fold mirror was sufficiently large that off

the shelf mounts had a center line height of more than 250 mm, so a custom mount was designed.) The

second difference is that the filter wheel capacity has been expanded to include a fifth filter position. A

five position filter wheel will now be used in both the red and blue channels.

Layouts of the VBI Red along with layouts of the Red and Blue channel combined are shown in the

following figures.

Figure 10: VBI Red Layout



Figure 11: VBI Red Layout Including ATST Light Feed

Figure 12: Left - VBI Red Layout on Coude Platform; Right – VBI Red & Blue Layout on Coude Platform (top down)



Figure 13: VBI Red & Blue Layout Including Light Feed

Figure 14: VBI Red & Blue Layout



3.1 FOLD MIRROR #1 MOUNT

Since the first fold mirror needs a clear aperture of >220mm in diameter in order to make the first fold of

the VBI Red optical layout, a common sized 254mm (10 inch) mirror will be used. An Aerotech

AOM110-10 mount can be used to hold this mirror. This off-the-shelf mount has a centerline distance

slightly less than the specified Coudé beam height above the optical benches of 250mm, so a riser mount

will be made. A COTS mirror mount will save some manufacturing time over a custom made mount.

The mount design of the first fold mirror is shown in Figure 15.

Fold Mirror 1 Mount Opto-Mechanical Design Requirements Compliance

Req. Matrix Num. Req. Description Requirement Goal As Designed Value

C303 X Tilt Adjustable (See Note 1) 0.08 arcsec (See Note 2)

C303 Y Tilt Adjustable (See Note 1) 0.08 arcsec (See Note 2)

Note 1: Requirement is to steer beam to within ±0.05 mm over a distance of >3 m.

Note 2: Pointing resolution per degree of adjusting screw - equivalent to 0.0012 mm @ 3000 mm.

Figure 15: VBI Red Fold Mirror #1 (Aerotech COTS)

3.2 FILTER WHEEL

The filter wheel assembly will now utilize a five, instead of four, position wheel. Everything else will

remain identical to the original design. The purpose of the fifth position is to allow the addition of an

alignment target/pinhole to the wheel and also to accommodate future upgrade expansion or allow the use

of the VBI as a context imager for another instrument that would require a different wavelength. There

was enough room on the previous Blue channel design to add another position without changing the

overall wheel diameter or the filter center distance. In addition, the original wheel was designed and



modeled with 13mm thick filters, but the actual filter thicknesses delivered for the Blue channel came in

at 7.4mm thick. This lighter weight for filters and shorter move distance (72° instead of 90°) yields

motion profile characteristics and performance very similar to the original four position design. The five

position filter wheel meets the same performance, accuracy and timing requirements as did the four

position filter wheel with minimal design impact. The filter wheel design is shown in Figure 16.

Filter Wheel Opto-Mechanical Design Requirements Compliance

Req. Matrix Num. Req. Description Requirement Goal As Designed Value

C19 Move time 0.54 sec. 0.34 sec. 0.145 sec.

C20 Accuracy ±0.1 mm ±0.05 mm 0.020 mm (See Note 1)

C299 X/Y Tilt 0.05º (See Note 2)

C21 Repeatability ±0.05 mm 0.018 mm (See Note 1)

C22 Cell diameter 70 mm min. 70 mm

C24 Clear aperture 65 mm min. 68 mm

Note 1: This is maximum theoretical mechanical error. Actual prototype testing shows accuracy and

repeatability to be within a single encoder count (5 arc seconds or 0.002mm).

Note 2: Wheel will be assembled and inspected to comply with required tilt angle.



Figure 16: VBI 5 Position Filter Wheel



4. SOFTWARE DESIGN

4.1 VBI RED CONTROL SYSTEM SOFTWARE

The VBI Red control system software is identical to that of the VBI Blue, but is deployed as an

independent system. This was done to 1) allow construction of the Blue channel to begin after passing its

CDR, 2) allow one channel to operate even if the other channel experiences problems and 3) to maximize

the flexibility of using the Blue and Red channels in conjunction with other instruments. For example,

the Blue channel can be configured to collect data in coordination with one instrument while the Red

channel can be configured to collected data in coordination with a different instrument.

The VBI Red system configuration differs slightly from the Blue channel to ensure user input parameters,

such as wavelength, are validated against the range of values specific to the Red channel.

4.2 SYNCHRONIZATION OF VBI BLUE AND VBI RED

Observations performed by the VBI Blue and VBI Red consist of one or more observation steps. Each

observation step represents a data acquisition that may consist of one or more camera exposures. The

VBI Blue and VBI Red are required to synchronize their camera exposures to within +/- 5ms. Since there

are no electronic trigger lines connecting the two instruments, achieving this level of synchronization

requires 1) alignment of observation steps and 2) execution timing.

Alignment of observation steps involves ensuring that the cadence of the steps defined for one instrument

is cohesive with that of the other. Execution timing involves starting those observation steps at precise

times and maintaining timing accuracy throughout their execution. In the following sections we will look

at how the VBI Blue, VBI Red, and other ATST systems are used to achieve synchronization and look at

a real example to help illustrate the process.

4.2.1 Alignment of Observation Steps

There are three types of alignment supported by the VBI Blue and VBI Red that may be selected when

building an experiment. The first type is observation start, which involves ensuring both the VBI Blue

and VBI Red start their first data acquisition at the same time. The second type of automatic alignment is

at the observation cycle level. This type of alignment involves making sure one channel does not repeat

its cycle of observation steps before the other channel has completed its cycle of observation steps. The

third type of automatic alignment must occur at the observation step level. This type of alignment

involves making sure the observation steps of one channel start at the same time as the corresponding step

of the other channel. In the next few sections we will look at an example of each of these alignment

types.

Alignment Example – Observation Start

As an example, imagine that we want the VBI Blue to take 6 frames at 10 FPS at three different

wavelengths (A, B, and C). The time allowed for moving mechanisms (i.e. filter change) between

wavelengths is 400ms, which is determined by finding the first multiple of the rate that is greater than or

equal to the minimum move duration of 333ms. The cycle for the VBI Blue would therefore consist of

three observation steps, each requiring 600ms for data acquisition (6 x 100ms per frame) and 400ms for

filter position change. Then suppose we want the VBI Red to take a single frame at 10 FPS at two

different wavelengths (D and E). The cycle for the VBI Red would therefore consist of two observation

steps, each requiring 100ms for data acquisition (1 x 100ms) and 400ms for filter position change.

To request observation start alignment, the user will select the option when building the experiment with

the VBI Explorer. Figure 17 below shows a prototype screen shot of the VBI Blue Explorer where the



user has selected observation start alignment. Notice that no other information regarding the observation

step offset is required when only start alignment is requested.

Figure 17: VBI Blue Explorer with Observation Start Alignment

With observation start alignment, the VBI Blue and VBI Red will only ensure that the observations are

started at the same time. After the observations are started, execution of cycles and their steps will

continue as fast as possible. Therefore, the ability for subsequent observation steps to remain in sync

completely depends on the duration of those steps, and is not checked by the VBI Explorer. Figure 18

below shows how the steps of these observations would align if we ran two cycles with observation start

alignment selected.

Figure 18: VBI Blue and VBI Red with Observation Start alignment

The VBI control systems will ensure the first camera data acquisition start time of the first observation

step is the same by using the ICS rendezvous service to obtain the agreed start time. Please refer to

section 4.2.2 for more information about this service. Once an ICS rendezvous start time is obtained, the

Visible Broadband Imager BlueExplorer

FixedCadence:

Data Acquisition Sequence:

Wavelength Frame Sets FramesRate

(fps)

Exposure Time

(seconds)Binning ROI

Offset

(seconds)

A 1 6 10 0.01 1x1 Full 1

B 1 6 10 0.012 1x1 Full 1

C 1 6 10 0.011 1x1 Full 1

Align for Synchronization:

5Number of Cycles:

Load from file:

Offsets (sec):--OR--

BROWSE

EDIT

SAVE

ALIGN

Observe Mode Configuration:

X

From file:

Start

CycleStep

D

A

Filter change

Filter change

B CFilter

change

EFilter

changeD

A

Filter change

Filter change

BFilter

change

EFilter

changeD

Filter change

EFilter

changeD

Filter change

EFilter

changeD

Filter change

EFilter

change

Filter change

500 1000 1500 2000 2500 3000 3500 4000 4500 50000



VBI Blue and VBI Red will use that time to program the “initial start time” of their cameras using the

CSS interface. Please refer to the SPEC-0098 CSS Functional Interface for more information about this

parameter and its use.

Alignment Example – Observation Cycle

In some scenarios the user may wish to synchronize the VBI Blue and VBI Red at the start of every cycle.

The observation cycle alignment type can be used for this purpose, and will ensure that the first

observation step of each cycle for the VBI Blue and VBI Red will begin at the same time. To accomplish

this, the system must take the VBI channel with the shorter total cycle duration and add a delay at the end.

When selecting this alignment type it is therefore necessary that the user enter the observation step

durations from the other instrument as a comma separated list so that the correct alignment calculations

can be performed. Figure 19 below shows a prototype screenshot of the VBI Blue explorer for the

example given before. Notice that the user has selected “cycle” type alignment and provided the offsets

from the VBI Red channel (500ms per observation step) as a comma separated list.

Figure 19: VBI Blue Explorer with Observation Cycle Alignment

When the user clicks the “Align” button, the VBI Blue Explorer will look at the offsets for the VBI Blue

and those provided for the VBI Red and determine which has the shorter cycle length. It will then present

the suggested alignment results to the user. For this example, the VBI Red has a shorter total cycle

duration of 1s (500ms x 2), compared to the VBI Blue cycle duration of 3s (1s x 3). Therefore the system


FixedCadence:



(fps)

Exposure Time


Offset

(seconds)

A 1 6 10 0.01 1x1 Full 1

B 1 6 10 0.012 1x1 Full 1

C 1 6 10 0.011 1x1 Full 1


5Number of Cycles:

Load from file:


0.5, 0.5

BROWSE

EDIT

SAVE

ALIGN


X

From file:

Start

CycleStep



will suggest adjusting the offset for the second step of the VBI Red to 2s. Figure 20 below shows a

prototype screen of the alignment results presented to the user.

Figure 20: VBI Blue Explorer Cycle Alignment Result

With observation cycle alignment, the VBI Blue and VBI Red will only ensure that the start of each

observation cycle is at the same time. After each cycle begins, execution of the observation steps will

continue as fast as possible. Therefore, the ability for subsequent observation steps to remain in sync

completely depends on how those steps are defined, and is not checked by the VBI Explorer. Figure 21

below shows how the steps of these observations would align if two cycles are run with observation cycle

alignment selected.

Figure 21: VBI Blue and VBI Red with Cycle Alignment

Alignment Example – Observation Step

In some scenarios the user may wish to synchronize the VBI Blue and VBI Red at the start of every

observation step. The observation step alignment type can be used for this purpose, and will ensure that

each corresponding observation step for the VBI Blue and VBI Red are started at the same time. To

accomplish this, the system must analyze each observation step for the two channels, and add a delay to

the end of the shorter steps to align with the longer steps. When selecting this alignment type it is

therefore necessary that the user enter the observation step durations from the other instrument as a

comma separated list so that the correct alignment calculations can be performed. Figure 22 below shows

a prototype screenshot of the VBI Blue explorer for the example given before. Notice that the user has

selected “step” type alignment and provided the offsets from the VBI Red channel (500ms per

observation step) as a comma separated list.

Alignment Calculator Results:

Data Acquisition Offsets (seconds):

0.5, 2.0

VBI Blue:

External Instrument:

SAVE TO FILE

X

No changes required

D

A

Filter change

Filter change

B CFilter

changeA

Filter change

BFilter

changeFilter

change

500 1000 1500 2000 2500 3000 3500 4000 4500 50000

EFilter

changeD

Filter change

EFilter

change



Figure 22: VBI Blue Explorer with Observation Step Alignment

When the user clicks the “Align” button, the VBI Blue Explorer will look at the offsets for the VBI Blue

and those provided for the VBI Red and for each step, determine which has the shorter duration. It will

then present the suggested alignment results to the user. For this example, the VBI Red has a duration of

500ms for step 1 while the VBI Blue has a duration of 1s for step 1. The system will therefore suggest

step 1 of the VBI Red be padded with 500ms so that step 1 for both channels will have a duration of 1s.

The same adjustment will be applied to the second step of the VBI Red, since it is 500ms shorter than the

second step of the VBI Blue. Figure 23 below shows a prototype screen of the alignment results

presented to the user.

Figure 23: VBI Blue Explorer Step Alignment Result


FixedCadence:



(fps)

Exposure Time


Offset

(seconds)

A 1 6 10 0.01 1x1 Full 1

B 1 6 10 0.012 1x1 Full 1

C 1 6 10 0.011 1x1 Full 1


5Number of Cycles:

Load from file:


0.5, 0.5

BROWSE

EDIT

SAVE

ALIGN


X

From file:

Start

CycleStep

Alignment Calculator Results:

Data Acquisition Offsets (seconds):

1.0, 1.0

VBI Blue:

External Instrument:

SAVE TO FILE

X

No changes required



With observation step alignment, the VBI Blue and VBI Red will ensure that the start of each

corresponding observation step occurs at the same time. Figure 24 below shows how the steps of these

observations would align if we ran two cycles with observation step alignment selected.

Figure 24: VBI Blue and VBI Red with Step Alignment

4.2.2 Establishing Initial Start Time for Cameras

Alignment of data acquisition blocks between the VBI Blue and VBI Red using the calculator tool

ensures that if the cameras start executing the sequence of blocks at the same time, the data acquisitions

will remain synchronized. Therefore, it is imperative that both the VBI Blue camera and VBI Red camera

be programmed with the same initial start time.

Several options were explored for establishing the initial start time. They included 1) User specified start

time, 2) ICS coordinated start time, and 3) ICS rendezvous. Option 1 was the simplest approach, and

only involved the user entering the desired start time before starting the observing task. The downside to

this approach was that picking a start time far enough in the future to accommodate the setup time of all

synchronized instruments could lead to wasted observing time (too far out), or possibly a missed

synchronized start (not far enough). Option 2 improved on Option 1 by having the ICS calculate the start

time only after all instruments involved in the synchronization were done with their setup. This solution

was sufficient for synchronizing the initial start of data collection for instruments, but did not support re-

establishing synchronization at different points during the observation. Option 3 was introduced by the

ATST Software Group as an improvement on Option 2 by allowing instruments to “rendezvous” with

other instruments at any time during the observation by communicating back with the ICS. Although

Option 2 was suitable for synchronization between the VBI Blue and VBI Red, Option 3 was chosen for

its flexibility to handle other synchronization needs that are likely to be required in future ATST

observation use cases.

Figure 25 below shows the context of the ICS Rendezvous solution. The Rendezvous component will be

used by all instruments requiring synchronization, and therefore it resides and is managed by the ICS.

The event service is used for communications between the observe script running in the instrument ICs

and the Rendezvous component in the ICS.

D

A

Filter change

Filter change

B CFilter

changeA

Filter change

BFilter

changeFilter

change

500 1000 1500 2000 2500 3000 3500 4000 4500 50000

EFilter

changeD

Filter change

EFilter

change



Figure 25: Context diagram for Synchronization via ICS Rendezvous

Figure 26 below shows a sequence diagram of the communications between systems in the ICS

Rendezvous solution. The ICS will instruct each instrument IC to first complete its setup activities, such

as moving mechanisms to their initial positions and programming the camera with data acquisition

settings. Once all instruments involved have completed setup, the ICS will instruct them to begin

execution of their data acquisition steps.

At this point, all instrument ICs that need to synchronize will communicate with the ICS Rendezvous

component via the CSF event service. They will post an event (atst.ics..rendezvous) stating

1) that they are ready to begin data collection (.action=rendezvous),

2) what other instruments they are expecting to synchronize with (.components[]),

3) how much time is required to start the camera (.offset), and

4) how much time to wait before timing out (.timeOut).

Upon receipt, the ICS rendezvous component will respond with an event (atst.ics.rendezvous)

acknowledging receipt of the request (.action=ack).

Once the ICS Rendezvous component has received the rendezvous request event from all instruments

involved in a synchronized observation, it will compute an initial camera start time by adding the current

time, the ICS Rendezvous response latency, and the longest time required to start the camera from any

instrument. This initial camera start time (.rendezvousTime) will be broadcast back to the instruments as

an attribute of an event (atst.ics.rendezvous) using the CSF Event service. Finally, the instruments will

receive the response event, program their cameras accordingly, and data acquisition will start on all

cameras at the same time.

Instrument Control System (ICS)

Observation Management System

VBI Blue Instrument Adapter VBI Red Instrument Adapter

Rendezvous

VBI Blue Instrument Controller VBI Red Instrument Controller

CSF Event Service

Rendezvous event Rendezvous event

Rendezvous event



Figure 26: Sequence diagram for VBI Blue and VBI Red synchronization using ICS Rendezvous

If the ICS does not receive all rendezvous requests from the instruments in the list before the shortest time

out period of any instrument, it will generate an event (atst.ics.rendezvous) indicating the rendezvous was

cancelled due to a time out (.action=timeOut).

The rendezvous request event (atst.ics..rendezvous) also provides the ability to cancel a request

(.action=cancel). If an instrument requests a cancel, the ICS will respond with an event

(atst.ics.rendezvous) acknowledging the cancel (.action=ack).

The ICS rendezvous functionality will be implemented as a service provided by the ICS and the user is

not directly involved in the details of the synchronization implementation (the Rendezvous component

and the specific events used). Because the service has not yet been implemented, some of the

implementation details may change in order to maximize efficiency and robustness. The details will be

documented in the relevant ICS documents (TN-0102, ICS Reference Design, SPEC-0113, Facility

Instrument Interface Specification, and TN-0152, Standard Instrument Framework).

ICS Rendezvous VBI Blue VBI Red

Start setup

Start setup

Setup complete

Setup complete

Start data acquisitions

Start data acquisitions

Wait for rendezvous

Wait for rendezvous

Start time = T

Start time = T

Data acquisitions complete

Data acquisitions complete

Start camera at T Start camera at T



5. TEST PLAN

5.1 INTERFERENCE FILTER TESTING

All filters will be tested using the Horizontal Spectrograph (HSG), a facility instrument installed at the

Dunn Solar Telescope (DST) in Sunspot, NM.

The steps of the filter acceptance testing are described below:

1. All used filters will be placed near a focal plane for the measurements.

2. A reference scan will be acquired using a broad, line selecting prefilter for the spectrograph. This is achieved by taking an image that encodes spectral information in one axis, and spatial

information along the other axis (slit), and subsequently stepping the slit to the next position in

the 2D spatial field of view and acquiring the next image.

A ‘super mean profile’ computed from this reference scan (see step 4 below) is compared against

a profile taken from a peer reviewed atlas profile in order to determine an absolute wavelength

axis for the used spectrograph and camera configuration, as well as the residual profile of the

broad, line selecting prefilter.

3. The broad, line selecting filter will be replaced with the interference filters that are to be tested for acceptance. Potentially, the slit length and range of the scan mechanism of the spectrograph does

not suffice for a test of the full interference filter aperture (Ø 70 mm). Therefore, the filter may have to be physically moved to mosaic the full aperture. This way, a grid of mosaic scan cubes

can be acquired; where the mosaic scan cubes slightly overlap.

4. The reference scan from step 2 above is used in the following computation:

a. The line curvature along the spatial axis inherent to the spectrograph is removed and, subsequently, all profiles along the spatial axis as well as from all scan steps are averaged

to create a ‘super mean profile’.

b. The filter profile of the broad, line selecting prefilter is removed from the ‘super mean profile’.

c. The 1D ‘super mean profile’ in return is used to create a synthetic 2D image that reproduces the line curvature along the spatial axis inherent to the spectrograph.

5. Out-of-band blocking over the spectral range will be tested by creating a mean profile for one mosaic scan, with camera read-out noise offset (‘dark noise’) subtracted.

6. Subsequently, all of the mosaic scan cube images are divided by the synthetic 2D image created in step 4b to remove the solar spectral signature in the data. Finally, remaining background -

estimated from unexposed ‘dark’ frames - is subtracted.

This creates the filter curve profiles. Filter transmission is encoded relative to the broad, line

selecting filter.

7. After correcting for the line curvature along the spatial axis inherent to the spectrograph, each of the filter curve profiles are fitted using the function:

( ) [ ]

( [ ] [ ] ⁄

)

In this case, the fit parameter P[1] corresponds to the filter central wavelength, P[2] corresponds

to the full width at half maximum (FWHM), and α corresponds to the number of cavities.



8. The resultant mosaic fit data are re-assembled into a full map of the filter for the parameter P[1] (central wavelength) and P[2] (FWHM), after solar structure remaining from step 6 has been

removed to best effort.

The preceding test method was developed and used for qualification of the VBI blue filters. The detailed

procedure and results can be found in ATST technical note TN-0164 VBI Filter Acceptance Test.docx.

5.2 INSTRUMENT TEST PLAN

The two channels of the VBI will be tested together. Testing of the VBI instruments will happen in

phases. Each phase consists of a development phase followed by a user acceptance test (UAT). UATs

are used to provide periodic exposure of the VBI and user interface to a limited set of users so that user

feedback may guide the software effort. All testing is performed to ensure compliance with the VBI

compliance matrix CMX-0001.

At the conclusion of each phase, a milestone is reached and a software release is announced. There are no

users of the releases in the early phases with the exception of the ATST software team who may elect to

use a particular release as a test tool to aid their own development effort. The release phases are: Alpha,

Beta, Lab, Engineering, Speckle, Integration phases (as needed), Shipping, and Operations.

5.2.1 Alpha Phase

Alpha phase includes the development of the mechanical assemblies, the VBI control system hardware

and software, and concludes with both channels of the VBI operable in a limited-functionality, stand-

alone configuration.

Mechanical

The mechanical tests ensure that the mechanical sub-assemblies meet VBI mechanical tolerance

specifications. These measurements will be performed during the final sub-assembly in Sunspot by the

VBI mechanical engineer. Fabrication of all VBI mechanical components is scheduled for completion by

March 2013.

Software

Software development occurs in parallel with mechanical construction and test. The VBI Red software is

identical to the VBI Blue software with the addition of the synchronization requirement as described in

section 4.2.

Alpha software development makes use of limited-functionality simulators for the Camera Control

Software (CSS) and Instrument Control Software (ICS) – these simulators are provided by the ATST

software team and are separate from the VBI effort. The Alpha release coincides with the completion of

all mechanical sub-assemblies.

The Alpha release is scheduled for March 2013.

5.2.2 Beta Phase

Development of the Beta release makes use of the VBI mechanical assemblies, instead of the simulators.

This work will be performed in the Tucson instrument lab and will incorporate the full CSS, the mini-

DHS, and a limited functionality ICS (provided by the ATST software group). Testing will focus on

individual sub-assemblies, and finally, all of the mechanical assemblies (minus optics) will be tested

together. The Beta release is scheduled for July 2013.



Utilizing the sub-assemblies early in the development of the instrument is advantageous because

operating the mechanical stages for a period of time allows the team to gain experience with the

assemblies and mitigates the risk of infant mortality.

The Beta release is scheduled for July 2013.

5.2.3 Lab Phase

The Lab phase finishes the instrument controller development and the data processing plug-ins; together

these components provide a fully functional stand-alone instrument using the project provided camera

simulator and mini-DHS.

The Lab release is scheduled for October 2013.

5.2.4 Engineering Phase

Following the Lab release, development will switch to speckle reconstruction development. During

speckle development, the project provided Engineering Camera, Tucson Camera Line, and Camera

Software Systems for Engineering Camera will be released. The engineering phase will conclude with a

fully integrated camera system using a Beta version of the speckle reconstruction engine. Speckle testing

will be done using simulated image files.

The Engineering release is scheduled for July 2014.

5.2.5 Speckle Phase

The Speckle phase will complete the speckle reconstruction development. Speckle testing will be done

using simulated image files. The complete VBI instruments will be assembled with the optics and optical

testing and a detailed optical alignment plan will be tested and documented.

The Speckle release is scheduled for January 2015.

5.2.6 Periodic Integration Phases.

At this point, the VBI will be fully functional using an engineering camera, the project provided camera

systems software, the project provided data handling system, the project provided instrument control

system, and the VBI software and mechanical assemblies. The project will be completing the final

versions of the Instrument Control System software and the Maui DHS. As these products become

available, along with updates to other software systems, they will be integrated and tested with the VBI

instruments.

The periodic integration phases are scheduled to be completed by April 2016.

5.2.7 Shipping Phase

The science cameras will be received in April 2016, along with the final release of the camera control

software. At this point, the final cameras will be integrated into the VBI in preparation of the VBI

readiness review. Integration testing with the latest releases of project provided software will be

performed and a full end-to-end test will be performed, including the final development and

documentation of the VBI installation and alignment plan.

The Shipping release will culminate in the VBI readiness review where the VBI team will demonstrate

complete compliance of the VBI instruments to the VBI Compliance Matrix CMX-0001. The review will

include a detailed test, installation, and alignment plan as developed during the Speckle and Shipping

phases. Installation and operations manuals will be deliverables at the readiness review.

The Shipping release is scheduled for October 2016.



5.2.8 IT&C Phase

Upon arrival at the telescope, the VBI instruments will be re-assembled in the instrument lab and the test

plan used for the readiness review will be repeated to ensure instrument readiness. Following these tests,

the VBI instruments will be installed into the Coude Lab as the first light ATST instruments. Training of

the operations staff will take place. Testing of the VBI channels will be repeated and proof that the

instruments meet the VBI Compliance Matrix CMX-0001 will result in operational readiness acceptance.

Upon proof of operational readiness, as defined by demonstration that both VBI channels are compliant

with the compliance matrix, the VBI team will have concluded their responsibilities to the project, and the

instruments will become the responsibility of the ATST project and will be handed over to the science

staff for science verification. At this point, the VBI instruments will be considered ATST facility

instruments.

5.2.9 Science Verification

The science verification plan is detailed in SPEC-0107 VBI CDD.docx. Science verification will test the

VBI instruments against the top-level science objectives for the instruments. Successful science

verification will result in the VBI being accepted for operation, at which point, responsibility for the VBI

instruments will be transferred to ATST Operations.



6. BUDGET

The VBI red construction budget is broken into three work packages: procurement (S-WANS3-222),

construction (S-WANS3-223), and integration / test / commissioning (S-WANS3-226). The top-level

budget is shown in Table 2 and the details are broken out in the tables that follow.

VBI-red Top Level Budget

S-WANS3-222 - Fabrication Drawings / Project Management $48,704

S-WANS3-222 - Filters $117,270

S-WXNS3-222 - Optics - Lenses / Mirrors $97,120

S-WANS3-222 - Controls & Mechanical $87,179

S-WANS3-223 - Construction $31,775

S-WXNS3-226 - Integration / Test / Commission $290,373

Total $672,422

Table 2

6.1 LABOR

Labor for the VBI is shown in Table 3. Upon a successful CDR, a change request will be submitted to the

project to encumber labor for the procurement, construction, and integration / test / commissioning phases

of the VBI red. Considerable savings in labor are achieved by “catching up” the construction of the red

channel to the blue channel, allowing for both to be assembled and tested together.

Workpackage Labor Start date End date

S-WANS3-222 Fabrication Drawings / Project

Management

$48,704 Sep-12 Apr-14

S-WANS3-223 Fabrication / Assembly $31,775 Sep-12 Jul-13

S-WXNS3-226 Test / IT&C $290,373 Jan-13 Feb-19

Total $370,852

Table 3

6.2 FILTERS

The VBI filter cost is shown in Table 4. The fourth filter wavelength has not yet been determined, but the

Science Working Group is expected to recommend a suitable wavelength by the end of 2012. This filter

is expected to be similar to the Red Continuum filter and is priced accordingly.

Filter Wavelength Cost

Hα 656.282 nm $51,540

Red Continuum 668.4 nm $22,380

TiO 705.8 nm $20,970

TBD TBD $22,380

Total Total $117,270

Table 4



6.3 OPTICS

The VBI blue CDR committee recommended the procurement of the optics blanks early to mitigate

availability and price risk. The objective lens blank has been procured as risk mitigation. The other

lenses use commonly available glass and the procurement will begin immediately upon successful

completion of the CDR.

The vendor that is manufacturing the VBI blue lenses has quoted the lenses for the VBI red. We were

able to have the vendor hold the manufacture of the blue lenses to wait for the red lenses. The lenses are

very similar to the blue lenses (the objective lens is identical with the exception of the coatings). By

holding the procurement of the blue lenses, the blue and red lenses can be manufactured together at a cost

savings.

The VBI blue lens cost is $83,550; the price of the red lenses was brought down to $74,530, a savings of

$9,020.

Lenses $69,750

Objective blank $4,780

Fold mirror 1 $12,040

Fold mirror 2 $700

2nd objective lens $9,850

Total $97,120

Table 5

6.4 CONTROLS & MECHANICAL

The camera is provided by the Project. The control, thermal, and electrical systems are identical to the

blue channel and the mechanical assemblies are identical with the exception of the first fold lens mount

and filter wheel as described in section 3.

Camera project

Control System $39,436

Thermal system $1,102

Electrical (from electrical sheet) $7,195

Mechanical (from mechanical sheet) $39,446

Total $87,179

Table 6

6.5 DATA HANDLING SYSTEM AND SPECKLE IMAGE RECONSTRUCTION

The addition of the VBI red instrument to the ATST instrument suite adds another channel to the Data

Handling System (DHS); this extra channel has already been included in in the DHS design and budget.

The DHS speckle reconstruction hardware was originally sized and budgeted to fully reconstruct every

burst of a single channel of VBI data. The speckle hardware was later de-scoped to provide near-real-

time reconstruction of every third burst of a single channel of VBI data, with the remaining bursts being

reconstructed over-night. This plan would have provided the horsepower for a reconstructed image

approximately every 9 seconds.



But, between the expected advances in GPU hardware and recent successes by the VBI team in speeding

up the core reconstruction algorithms, the VBI team hopes to obtain higher performance from the

budgeted GPU hardware than originally anticipated. Continued development of the parallelization of the

speckle algorithms is ongoing, and it is difficult to predict the final capability of the reconstruction

engine, but the team is hopeful that it will be possible to reconstruct every 2nd

or 3rd

burst of both VBI

instruments simultaneously. This will produce one reconstructed image every 3 to 4.5 seconds. It is also

important to note that the system is scalable, allowing improved performance with the simple addition of

more GPU blades in the speckle hardware system in the future.

6.6 BILL OF MATERIALS

Qty Part Description Filters

1 Hα

1 Red Continuum

1 TiO

1 TBD

Optics

1 Objective Lens

1 FM1 254mm Flat Mirror

1 Field Lens

1 FM2 100mm Flat Mirror

1 Collimator Lens

1 Image Lens

1 2nd image lens

Mechanical Components

1 Objective Lens Mount (275mm)

1 Fold Mirror 1 Mount (254mm)

1 Field Lens Mount (50mm)

1 Fold Mirror Mount 2 (150mm)

1 Collimator Lens Mount (75mm)

1 Collimator stage

1 Collimator stage bench mount

1 Collimator stage motor

1 Filter Wheel

1 Filter Wheel Assembly Tool

1 Imaging Lens Mount (75mm)

1 Camera mount

1 Camera stage x/y bracket

2 Camera stage

2 Camera stage motor

1 Camera stage bench mounting plate

28 Optical bench hold-down mounts w/ hardware

1 Proportioning valve

2 Coolant hoses



Optical bench cables

1 Collimator Stage motor cable

1 Collimator Stage encoder cable

1 Collimator Stage limit switch cable

1 Collimator Stage brake cable

1 Filter Wheel Motor cable

1 Filter Wheel Encoder cable

1 Proportioning valve cable

1 Temperature sensor cable

1 Camera x stage motor cable

1 Camera x stage encoder cable

1 Camera x stage limit switch cable

1 Camera x stage brake cable

1 Camera y stage motor cable

1 Camera y stage encoder cable

1 Camera y stage limit switch cable

1 Camera y stage brake cable

Control System

1 Instrument computer

1 Instrument computer monitor

1 Instrument computer keyboard

1 Instrument computer mouse

1 24V power supply

1 24V distribution panel

1 Delta Tau UMAC controller chassis

1 UMAC power supply

1 Power PMAC card

2 4 axis PWM card with quadrature encoder reader

1 Universal serial card with BISS reader

1 Delta Tau UMAC drive chassis

2 Dual 4A motor Amp

1 8A motor Amp

1 Regeneration resistor

1 120V power distribution strip

Control system cables

4 PWM cables

3 24V drive cables

1 Copley 24V Amp

1 Copley PWM cable

1 Copley 24V cable

1 208/120V power cable

3 IEC 320 power cable

1 USB cable



1 Misc. 24V cables to encoder cards

Coude Lab Bench

1 Optical bench

4 Optical bench legs

4 Optical bench beam support interface clamps

1 Optical bench seismic restraint kit

2 Optical bench power distribution strip

1 Optical bench cable raceway / wiring tray



7. SCHEDULE

The supplemental documents contain an excerpt from the ATST project schedule containing only those

items that pertain to the VBI red and blue instruments. The dependencies on the other aspects of the

project, particularly the telescope software systems, were presented in the VBI blue CDR and remain

unchanged except for minor schedule adjustments.



8. HAZARD ANALYSIS

The Hazard analysis for the VBI blue is also applicable to the VBI red, since the designs are almost

identical. Please refer to SPEC-0107 VBI CDD.docx for the blue channel hazard analysis.

The only hazard identified as being different from the VBI blue channel is the glint hazard, since the

power density in the red beam is higher than the power density in the blue beam primarily due to the

broader wavelength range. Table 7 shows the glint hazard analysis for the red channel of the VBI at the

focus. Blink time is assumed to be 250ms, so the risk of eye damage is minimal. Worst-case values were

used for these calculations.

An additional point, which is the result of overlapping the blue and red channel optics on the same

benches, is that the focal points of the beams are now physically difficult to get to. In the original blue

channel design, it was conceivable that a person could put their eye into the beam, but with the current

design, a person would have to lie on a busy optical bench to get their eye into a focus.

Specific Heat Capacity

Substance cp [J·g−1·K−1] density [g·cm−3]

Skin 3.48 1.2

Power at VBI Focus [W] 13.305622

Diameter of VBI Focus [cm] 4.3

Power / area at VBI Focus [W·cm-2] 0.916238188

Skin Area considered [cm2] 1

Skin Depth considered [cm] 0.1

Skin Volume considered [cm3] 0.1

Skin Mass considered [g] 0.12

Minimum Time regarded safe [s] 20

Maximum Temperature

increase regarded safe [K] 4

Time to critical increase [s] 1.823106722 Hazard

Table 7



9. PROJECT MANAGEMENT

The VBI blue CDR committee recommended that the VBI be treated as a subcontractor with the

implementation of clear interfaces between the project and the VBI team. The committee also

recommended the implementation of earned value tracking to detect cost and schedule variances. Both of

these recommendations have become a reality for the VBI blue and red instruments. Formal procedures

for change requests, technical directives, and controlled interfaces documents have been established. In

addition, a project-wide earned value system has been implemented; the VBI budgets and schedule

updates are input into the system monthly; monthly variance reports are generated, and this enables

accurate budget and schedule tracking.

The VBI red WBS can be seen in the project schedule. The Fabrication of the VBI components will take

place in the Sunspot machine shop where Scott Gregory will supervise the machining and assembly of the

sub-assemblies. Bill McBride and Andy Ferayorni will take the sub-assemblies (with the exception of the

optics) to the Tucson instrument lab for software testing and qualification. The sub-assemblies will also

be tested with the ATST high level software systems being developed in Tucson.

Final instrument assembly will take place in either Sunspot (where the Hilltop lab, Dunn telescope, and

Sunspot Instrument lab are available) or in the new labs being constructed in Boulder.

The final instrument cameras will be delivered to the VBI team by the project in early 2016. Integration

of the cameras into the VBI instruments and final verification will take place in either Sunspot or Boulder.

Following final verification, the VBI instruments will be transported to Hawaii to be integrated into

ATST as the first light instruments. See section 5 for further details.



10. RISK ASSESSMENT

ATST Spec 37 defines the project approach to risk analysis and mitigation. A summary of the approach

can be found in SPEC-0107 VBI CDD.docx.

10.1 VBI RISK REGISTER

The VBI red risk register spreadsheet (provided as a separate document) contains a distillation of the

unmitigated risk items for the VBI red instrument from the ATST project risk register.

The primary risks to the VBI red instrument remain the manufacturability of the filters, the cost and

feasibility of the speckle reconstruction engine, key person loss, and shipping damage. Additionally, the

project carries risk with the integration of the instrument into the facility.

All of these risks are being mitigated with early development and integration of the VBI instruments. In

addition, the VBI has been selected as the early first-light instrument to work through integration

problems at the summit earlier than was previously planned.

Documents

Visible Broadband Imager Red Channel Critical Design Definition · 2020. 1. 22. · The F/20.3 focal plane is tilted 4.29˚ (due to the tilted field provided by the ATST) and is fixed