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Spacebel, 5/04/05 Page 1
LYRA Instrument and Data Manager
Software Requirements Analysis
Spacebel, 5/04/05 Page 2
Agenda
• Concept description• LIM requirements presentation (SBI)• LDM requirements presentation (SBI)• Interface issues • Open questions
Spacebel, 5/04/05 Page 3
PROBA 2 orbit
• Sun synchronous• LTAN: 6:00• See emails F.Teston for details
eclipse duration
00/01/00 0:00
18/07/00 0:00
03/02/01 0:00
22/08/01 0:00
10/03/02 0:00
26/09/02 0:00
14/04/03 0:00
10/10/06 0:00 28/04/07 0:00 14/11/07 0:00 01/06/08 0:00 18/12/08 0:00 06/07/09 0:00
date
tim
e [s
]
•Eclipses: • approximately 3 months eclipse season• rest of the year: no eclipses• maximum eclipse duration approx. 1100 sec.
Concept description
Spacebel, 5/04/05 Page 4
PROBA 2 Pointing
1. Frames definitions
Sun frame (Xsun, Ysun, Zsun)Xsun is spacecraft-sun axis ( = unit(Rsun – Rsc) where Rsun is the
apparent sun vector from the Earth (Sun ephemeris) and Rsc is the spacecraft position vector. If S/C position is unknown onboard, Rsc is set to zero.
Ysun is perpendicular to Xsun, in the plane defined by Xsun and the normal to the ecliptic plane, pointing towards the northern hemisphere.
Concept description
Earth Sun
Rsc
Rsun
Xsun
Ysun
Spacebel, 5/04/05 Page 5
S/C Fixed Body Frame
Concept description
Mechanical frame (Xmech, Ymech, Zmech)... With respect to S/C
Payload frame (Xpl, Ypl, Zpl)...With respect to SWAP
Spacecraft fixed body frame (Xbof, Ybof, Zbof) ... Related to Payload frame, but origin in S/C COG. Reference frame for spacecraft attitude control.
Spacebel, 5/04/05 Page 6
PROBA 2 Pointing
2. Pointing in observation mode
four (baseline, up to 8 possible) large-angle rotations of 90° (or 360° / number of rotations) attitudes are commanded over one orbit in order to avoid blinding of the star trackers; For the rest of presentation: baseline number of rotations assumed) the timing of the manoeuvres is such that the exclusion angles from the star trackers towards the earth are maximised; (performed on board -> cont. variation) the 90° manoeuvres will take a few minutes and will be centred around these optimal switching times; the time until the next rotation is continuously provided; paving rotations are defined in the original sun frame.
Illuminated face ofthe Earth
left
left
left
left
Concept description
Spacebel, 5/04/05 Page 7
PROBA 2 Pointing
2. Pointing in observation mode
The observation mode is commanded as follows:• the large rotation is commanded as a quaternion in the SUN frame:
[q1cmd, 0, 0, q4cmd];• the commanded large angle rotations will be taken from a list (of maximum 8) quaternions, configured by the ground;• the index of the currently used large angle rotation will continuously be provided;• the paving rotation is commanded as a quaternion in the SUN frame:
[0, q2paving, q3 paving, q4 paving]
Paving rotation around YSUN and ZSUN
Large-angle rotation around XSUN
SUN
SUN*
REF
Concept description
Spacebel, 5/04/05 Page 8
Concept description
• LIM mode diagram
Acquisition Warm-
up
Off
Idle
FDIR/TC FDIR/TC
FDIR
TC
TC/auto TC/auto
TC/auto
Spacebel, 5/04/05 Page 9
Concept description
• Mode simplification:– Off (CSL/ROB survival mode -> idem SWAP)– Idle (CSL/ROB night mode -> idem SWAP)– Warm-up (CSL/ROB stand-by mode -> idem SWAP)– Acquisition (CSL/ROB nominal modes)
• Modes not implemented in SWIM:– First swtich on: will be performed by uploaded procedure– Bake-out mode: uploaded or onboard procedure – Calibration mode: uploaded or onboard procedure, using
manually the imaging mode with different pointing configurations
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• Sequence diagram Nominal observation
Concept description
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Concept description
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Concept description
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Concept description
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•Open questions
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• Interace issues