Transcript Document 7680692

The Liverpool Telescope
Iain Steele
Liverpool John Moores University
Basic Specification
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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
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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
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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
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“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
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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
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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!