The Liverpool Telescope

Iain Steele

Liverpool John Moores University

Basic Specification

• Fully opening enclosure• 2.0 metre f/10 ALT/AZ• 2 degree / second slew speed• A&G box with deployable, folding mirror, allowing support

of upto 5 instruments• Instrument change time < 30 seconds• Common User Facility (typically 40-50 science

programmes from around 30 different institutes, allocated by TAC’s)

• Fully Robotic (no night time supervision apart from start of night photometricity check, weekdays there is a daytime daily visit)

Relationships

• LT is owned and operated by Liverpool JMU• Manufacturing facility (TTL) was owned by

Liverpool JMU, now owened by Las Cumbres Observatory

• Faulkes Telescopes were owned by Dill Faulkes, now owned by Las Cumbres Observatory

• Three telescopes still part of Robonet-1.0, and Liverpool JMU has an allocation of observing time on the Faulkes Telescopes until 2010 at least.

Open Air enclosure gives problems with scattered

moonlight

Operating Modes

• “Science Control Agent” - phase 2 database driven

• Background mode (does standards!)– Nothing to schedule– Seeing > 3 arcseconds (or unknown)– Something is broken (e.g. out of focus!)

• Target of Opportunity Mode– Immediate abort of current observing– Driven by scripts

Phase 2 database

• Specifies the observation (“what not how”)• Current Methods of data entry:

– Phase 2 forms via email– Menus for a specific science programme– RTML via unix socket

• Future Methods of data entry:– User Tool (web based - Java Web Start)– RTML via Web Services

Observation Types

• Flexible– Any time after a start date the conditions are met.

Once only.

• Monitor– Repeat at an interval with accuracy defined by a

window fraction

• Ephemeris– Once only, at a specified phase

• Fixed– At a specific time (with some error attached)

Scheduling from phase 2

• Lateness• Height• Priority• Missed Period• Darkness matching• Seeing matching• Slew• Transit• Allocation Fraction

Targets of Opportunity

• a client script (csh) running at the telescope (e.g. GRB followup)

• An intelligent agent submitting Robotic Telescope Markup Language with the appropriate priority flag (e.g. exoplanet microlensing)

• Make it as simple or as complex as you like…

RTML Example<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE RTML SYSTEM "http://www.estar.org.uk/documents/rtml2.1.dtd"><RTML version="2.1" type="request"> <Contact> <Name>Chris Mottram</Name> <User>TMC/estar</User> </Contact> <Project>agent_test</Project> <Telescope/> <IntelligentAgent host="localhost" port="1234">1</IntelligentAgent> <Observation> <Target type="normal"> <TargetName>test</TargetName> <Coordinates> <RightAscension units="hms" format="hh mm ss.ss">01 02 03.00</RightAscension> <Declination units="dms" format="sdd mm ss.ss">+45 56 01.00</Declination> <Equinox>J2000</Equinox> </Coordinates> </Target> <Device type="camera" region="optical"> <Filter><FilterType>V</FilterType></Filter> <Detector> <Binning rows="2" columns="2"/> </Detector>ratcam</Device> <Schedule> <Exposure type="time" units="ms">1000.0</Exposure> </Schedule> </Observation> <Score>0.0</Score></RTML>

Instrumentation (mixture of general purpose and science

specific)• Current

– RATCam - optical CCD camera– SupIRCam - JH near-IR camera– RINGO - optical polarimeter

• Near Future– Meaburn Spectrograph– FRODOSpec– Fast Readout CCD?

• Later– Wide field CCD?– SupIRCam2? (wider field, K band, grism spectra)

Common Features Between Instruments

• Completely independant• Same command set (e.g. CONFIG, DAY_CALIBRATE,

NIGHT_CALIBRATE, TWILIGHT_CALIBRATE,

WAVELENGTH_CALIBRATE, EXPOSE)• Knowledge of calibration procedures built into the

instrument control system• Electrical power kept running 24/7• No precision servo mechanisms (obtain precision

via mechanical means)• Daily reboot of control computers• Problems with cooling…

RATCam Specification

• 2048 x 2048 pixels• 0.135 arcsec/pixel• Read noise < 8 electrons• Binning 1x1, 2x2, 3x3, 4x4• No windowed modes• Bad pixel mask available• Heavy saturation results in charge

persistance and observations causing this will not be allowed

RATCam Filter Set

• “Sloan” u’ g’ r’ i’ z’

• Bessell B V

• H• Transformations to standard Sloan and

Cousins systems are available on web page.

RATCam Calibrations

• Flat fields are obtained automatically in morning twilight. On average around 5 exposures through 5 filters are obtained, meaning that we get though the complete set (binned 1x1 and 2x2) about every 3-4 days.

• Landolt photometric standard fields are observed (twice per filter) at a range of airmasses every 2 hours.

RATCam Data Pipeline

• End of night pipeline– Debiases based on overscan region– Trims overscan– Flat fields based on latest flats

• Data provided to allow user to– Defringe– Apply a bad pixel mask

SupIRCam

• Now back on telescope and much improved following engineering work

SupIRCam specification

• 256 x 256 pixels HgCdTe• 0.4 arcsec/pixel (1.7 arcmin FOV)• Read noise = 26 electrons• Dark current = 50 electrons/second• JH only• Linearity ~ 2% • pixel-pixel sensitivity variations 2% (J), 4.5% (H)• Possible J band red-leak gives higher sky

background in J than H

SupIRCam observing

• Exposure times =1,2,5,10,20 and 50s• Dither patterns with 1,2,5 and 9 pointings with

7 arcsec offsets. Offset time = 10 seconds (was 20 seconds)

• Option to do a separate sky field altogether• An equal length dark frame is always taken

before and after the dither.• Photometric standards (UKIRT FS list) every

three hours

SupIRCam data reduction

• Currently no pipeline• Chris Gerardy (IC) has a prototype pipeline

that can handle the bias slopes in old SupIRCam data

• For new data, standard Starlink or IRAF routines should be sufficient– Dark subtraction using mean of before and after

darks– Create flat field from median filtering dithered

science frames and divide in

RINGO

• Optical polarimeter

RINGO in action (GRB060418; P<8%)

RINGO Specification

• “V+R” filter (4600 - 7200 Angstroms)• Same CCD as RATCam but only cooled to -

10 degC (dark current ~ 1 electon/sec)• Note ability to measure optical polarization

variations on short (seconds - minutes) timescales is unique

• Saturation limit V~5 (V~3 with lots of very short exposures)

RINGO Sensitivity

Meaburn Spectrograph

• On telescope, optics fixed. Needs commissioning and automated acquisition routines implementing

• Four, fixed wavelength ranges

• 4 Angstrom resolution

• 49 x 1.7 arcsec fibres

• 512 x 512 pixel array, -15 degC

Example Meaburn Spectrum

FRODOSpec

• Blue Arm 3800 - 5750Å, R = 2300, 6300• Red Arm 5750 - 9000Å, R = 1780, 5530• Fixed central wavelengths• 11 x 11 lenslet array (0.9 arcsec “pixels”)• Argon and Xenon lamps• 4k x 2k detectors cooled to -100 degC• Under construction in Liverpool, ships to La

Palma in Summer 2007.

Lab Test Spectra

Summary

• LT is now generally working well. There is a good variety of instrumentation and this is important for a faciliy (rather than experiment) based obervatory.

• You need to keep developing new instrumentation to keep competitive

• Devolve as much of the detail of the instrument to its own systems (standard command set, calibration details)

• Avoid common systems (but use common designs!)• Avoid moving parts where possible

– If you can’t, avoid the need for precison– If you need precision, use mechanical rather than

software/electronic technqiues

• Klaus’ list of pre-requisites was a good one!