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The Liverpool Telescope

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

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The Liverpool Telescope

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  1. The Liverpool Telescope Iain Steele Liverpool John Moores University

  2. 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)

  3. 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.

  4. Open Air enclosure gives problems with scattered moonlight

  5. 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

  6. 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

  7. 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)

  8. Scheduling from phase 2 • Lateness • Height • Priority • Missed Period • Darkness matching • Seeing matching • Slew • Transit • Allocation Fraction

  9. 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…

  10. 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>

  11. 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)

  12. 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…

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. SupIRCam • Now back on telescope and much improved following engineering work

  18. 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

  19. 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

  20. 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

  21. RINGO • Optical polarimeter

  22. RINGO in action (GRB060418; P<8%)

  23. 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)

  24. RINGO Sensitivity

  25. 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

  26. Example Meaburn Spectrum

  27. 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.

  28. Lab Test Spectra

  29. 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!

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