Transcript KMOS operations and performance Presentation to the KMOS ESO IST, 10th May 2006

KMOS operations and
performance
Presentation to the KMOS ESO
IST, 10th May 2006
KMOS operations
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Observation preparation
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During the observations
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Configuring the arms
Sky subtraction options
Source acquisition
Observation of calibration stars
After the observations
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Daytime calibration
Post processing steps
KMOS IST meeting, ESO, 10tth May 2006
Setting the requirements
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Performance requirements are specified
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Essential
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Optimal
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Achieving these represents a significant scientific
gain and our goal is for the design to meet these
Desirable
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the design must be meet these requirements and
is verified against them
to be met if can be met with minimal impact on
the design/cost/schedule
Not all requirements have multiple levels
KMOS IST meeting, ESO, 10tth May 2006
General operations principles
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Building on experience with NIR IFU
instruments within the consortium
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SINFONI, GNIRS, UIST
Building on ESO experience with the aim
of producing an operational model
compliant with ESO standards and
practice
KMOS IST meeting, ESO, 10tth May 2006
Preparation of the
observations
Performance information
Configuration of the arms
Sky subtraction mode
Req 3.5.1: Throughput
KMOS IST meeting, ESO, 10tth May 2006
Detector module
Hawaii RG2 arrays from Rockwell (2048x2048 pixels),
results from Gert Finger
KMOS IST meeting, ESO, 10tth May 2006
KMOS IST meeting, ESO, 10tth May 2006
KMOS IST meeting, ESO, 10tth May 2006
Req 3.5.2: Instrument thermal
background
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Design follows best practice
of light tight croystat, use of
baffling.
KMOS IST meeting, ESO, 10tth May 2006
Sensitivity model
KMOS IST meeting, ESO, 10tth May 2006
Sensitivity model
KMOS IST meeting, ESO, 10tth May 2006
Arm configuration
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24 arms (req 3.5.12) are configured within
7.2’ field (req 3.5.9) using KARMA
Fields of view
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2.8arcsec x 2.8arcsec IFU fields (Req 3.5.10)
0.2arcsec in both spatial directions (Req 3.5.9)
Anamorphic magnification in the IFUs
KMOS IST meeting, ESO, 10tth May 2006
Arm configuration
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Arms are configured using KARMA
Automatic configuration based on rules
and optional manual configuration
Input catalogue:
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source positions with priority
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Band 1 – highest priority, must be observed
Band 2 – reduced priority, should be selected
over a Band 3 object
Band 3 – lowest priority, could be deselected
with little loss to the programme.
KMOS IST meeting, ESO, 10tth May 2006
Arm configuration
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Input catalogue:
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Positions of objects with priority
Positions of reference stars for acquisition
Position of guide star
Optional positions for sky with priority
Optional positions of bright stars to avoid
Input image:
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Required
Not used to derive object positions
Used to identify sky positions
KMOS IST meeting, ESO, 10tth May 2006
Arm configuration
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Set of rules
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No collisions between arms
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No vignetting
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Never violated
Closest approach includes margin for atmospheric
refraction
May be violated, flag set in the file header
Will avoid bright objects (K<12) hitting an arm
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May be overridden in ‘manual’ mode
KMOS IST meeting, ESO, 10tth May 2006
Requirements on arm
positioning
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Req 3.5.15: Close packing of target fields
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≥ 10 fields within 1arcminute
Req 3.5.16: Simultaneous observations
of close packed fields
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≥ 3 fields within more than one 1arcminute
field
≥ 10 fields within more than one 1arcminute
field, within a restricted patrol field
KMOS IST meeting, ESO, 10tth May 2006
Access to clusters
KMOS IST meeting, ESO, 10tth May 2006
Requirements on arm
positioning
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Req 3.5.17: Closest approach of target
fields
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12 pairs of two target fields within 6arcsec
edge-to-edge
Best seen in the mapping mode
KMOS IST meeting, ESO, 10tth May 2006
KMOS IST meeting, ESO, 10tth May 2006
KMOS IST meeting, ESO, 10tth May 2006
Fixed arm configurations
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For observations of the calibration source
For observations of calibration stars
For mapping mode
KMOS IST meeting, ESO, 10tth May 2006
Mapping mode (req 3.5.16)
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Arms set to a regular
grid on the sky
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Single configuration, fixed
by arm mech. design
Telescope offsets to
execute a jitter pattern
0.75 square arcmin in 16
moves
TBD whether available in
service mode
KMOS IST meeting, ESO, 10tth May 2006
Sky subtraction modes
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Four modes of sky subtraction provided
for in the PDR design
Experience from other instruments being
brought to bear
Flexibility to explore the most efficient
options during commissioning
Sky subtraction mode impacts the flatfield requirements
KMOS IST meeting, ESO, 10tth May 2006
Sky Subtraction: Offsetting Objects
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Single set of objects is
offset between arms
50% of time spent on
source; 50% on sky
Object and sky observed
along same optical
path/same pixels
Flat-field accuracy
requirements ~1%
KMOS IST meeting, ESO, 10tth May 2006
Sky subtraction: Offset frames
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Object is offset between
arms
Observing objects in the
‘offset’ beam improves
efficiency, but may be hard
to achieve in real sources?
Object and sky observed
along same optical
path/same pixels
Flat-field accuracy
requirements ~1%
KMOS IST meeting, ESO, 10tth May 2006
Sky Subtraction: Source fields
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Sky signal obtained from the
periphery of the IFU fields
Highly efficient
Flat-field accuracy
requirements ~0.1%
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Achieved through a
combination of flat-field
observation and scaling OH
lines
KMOS IST meeting, ESO, 10tth May 2006
Subtraction: Sky arms
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Arms not assigned to
objects are used to observe
sky
Requirements on flatfielding are that sky signal
must be calibrated to 0.1%
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Achieved through
combination of flat-field and
post-processing
KMOS IST meeting, ESO, 10tth May 2006
Other configurable parameters
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Exposure time
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Time to reach the background limit TBD, but
around 600s
Non-destructive read-out will be standard
Spectrometer
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User selected wavelength band
The same grating and appropriate filter
selected for all three spectrographs
Achromatic spectrograph, so no focus
KMOS IST meeting, ESO, 10tth May 2006
Spectroscopic modes
Req 3.5.5: Total wavelength coverage
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At PDR, four options: IZ, J, H, K
Extension to 0.8um is optimal requirement
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i.e. coatings, IQ etc are acceptable
Requires additional IZ grating and filter,
discussed later…..
Additional, broader l coverage (JH/HK)
gratings with lower R TBD during FDR
phase (req 3.5.20)
KMOS IST meeting, ESO, 10tth May 2006
Spectroscopic modes
3.5.21: Wavelength multiplex advantage
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‘Optimal’ requirement and initial KMOS
concept to configure 3 spectrometers
with different gratings, different DITs
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Opted for single detector controller, therefore
different DITs not possible
Multi-grating option not implemented
KMOS IST meeting, ESO, 10tth May 2006
3.5.19: Spectral resolving power
5000
4500
4000
spectral resolving power
3500
3000
2500
2000
Spectral resolving power secondary to wavelength coverage
1500
IZ:0.8-1.05um; J:1.05-1.37um;
H:1.45-1.85um; K:1.95-2.50um
1000
500
0
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
wavelength (nm)
KMOS IST meeting, ESO, 10tth May 2006
During the observations
Source acquisiton
Calibration stars
Observational efficiency
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Req 3.5.8: Desirable requirement for
>85% efficiency in one hour gives
9minute budget
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Instrument configured during 6min telescope
preset
Predicted 1min for observations of reference
objects during acquisition. Budget ~3min.
Additional ~1min required if reconfiguring
arms for different science targets
KMOS IST meeting, ESO, 10tth May 2006
On loading the arm
configuration
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Arm positions recalculated for the
airmass at the start of observations
In the case of a failed arm, the
requested rotation of the field is altered
until the allocation of arms to high
priority targets is optimised
KMOS IST meeting, ESO, 10tth May 2006
Arm failure and related responses
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Impact of an arm failure
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1/24 loss of efficiency measured simply by
non-availability of an arm
Thoughtful arm design has ensured that one
arm does not block others
Modelling with KARMA suggests ~1 objects
no longer accessible in ‘standard’ clusters.
Can be improved by reselecting rotation
KMOS IST meeting, ESO, 10tth May 2006
Acquisition
with KMOS
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Acquisition to
±(0.5,0.5) spatial
elements
Repeat
positioning to
<±0.2arcsecs
KMOS IST meeting, ESO, 10tth May 2006
Acquisition Steps
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Configure KMOS during telescope preset
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For three bright reference sources or for
science field
Acquire guide star
Targets should be acquired now
Observe, determine centroids
Apply systematic offset as required
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Ignore small (<~0.2arcsec) random offsets
If sources are not seen, start a different OB
KMOS IST meeting, ESO, 10tth May 2006
Acquisition
with KMOS
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In visitor mode
only (req 3.5.11)
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Small (< 1 field)
adjustments of
arms subject to
rules
KMOS IST meeting, ESO, 10tth May 2006
What changes during the
observations?
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Nothing
No movement of the arms
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Not for sky positions
Not for atmospheric refraction
No flexure compensation
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Not for spectroscopic shifts
Not for image movements/flexure
NB: change from Phase A concept
KMOS IST meeting, ESO, 10tth May 2006
More on Spectral flexure
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Sources
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Flexure of the pseudo-slit relative to the
spectrograph
Flexure of the detector+mount relative to slit
Flexure of the grating
Design has flexure within acceptable limits
(req 3.5.23: <0.2pixels)
If as-built flexure is unacceptable, calibrate
with OH lines
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Technique developed on SINFONI
KMOS IST meeting, ESO, 10tth May 2006
More on image movement
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Sources
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Bulk motion of the instrument relative to the
Nasmyth flange
Relative movements of the arms
Relative motions of the arms cannot be
compensated
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Arm design meets the requirements on flexure
NB not a peculiarity of the arms
KMOS IST meeting, ESO, 10tth May 2006
More on image movement
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Bulk motion of the cryostat
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Produces shifts in the images
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Blind co-addition of images will result in combined PSF
of 0.49arcsec over 1 hour in 0.4arcsec seeing
Compensated by post-processing of images
BUT NB this does not include detector cross-talk and
assumes ZD>10degrees
Produces a shift of the spectral lines in conditions
of the best seeing
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5% increase in line width
±0.23pixels movement of the centroid
NB this does not affect subtraction of sky lines
KMOS IST meeting, ESO, 10tth May 2006
Observation of calibration stars
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Fixed arm configuration
Telluric standard from one arm
Option to repeat once per spectrograph
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Three arms deployed into the field
offset telescope
Flux calibration
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Via the telluric standard or a flux standard
Relative throughput of arms scaled from sky
background
KMOS IST meeting, ESO, 10tth May 2006
After the observations
Daytime calibration
Post processing steps
Calibration system
KMOS IST meeting, ESO, 10tth May 2006
Calibration lamps
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Dedicated calibration
unit containing
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Two tungsten lamps
for flat fielding (one
plus spare)
One argon lamp for
wavelength
calibration
KMOS IST meeting, ESO, 10tth May 2006
Flat-fielding
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Continuum source in the calunit
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Modelled spatial uniformity:
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Provide spatially+spectrally smooth field
Few-% (possibly better…..)
Sphere to be built and tested during FDR
phase
To remove vignetting function, flat-field
on sky with arms in deployed position
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Twilight flats provided for, but not routine
KMOS IST meeting, ESO, 10tth May 2006
Wavelength calibration
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Argon arc lamp expected to provide
wavelength calibration to <0.1pixel
(±2.5kms-1)
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req 3.5.24 on wavelength scale accuracy met
Requirement (3.5.22) on velocity
precision of ±10kms-1 met
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Including allowance for predicted movement
of the centroid in best seeing
KMOS IST meeting, ESO, 10tth May 2006
Image reconstruction: in the lab
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Spatial calibration established in the lab
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Spectral curvature
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Offsets of the IFU slitlets
KMOS IST meeting, ESO, 10tth May 2006
Image reconstruction: in the lab
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Test facility for use in integration lab
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Slit mask projects to the focal plane and can
be observed by each IFU in turn
KMOS IST meeting, ESO, 10tth May 2006
Image reconstruction: on telescope
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Spatial calibration established most
efficiently in the lab
Changes within and IFU not expected
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Would be as result of movements of
monolithic mirrors
Flexures may cause shift of the long
slit (from 8 IFUs) relative to detector
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Detectable from flat-field
Would not affect the reconstructed image
KMOS IST meeting, ESO, 10tth May 2006
Image
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n
recon :
on the telescope
No access to the front of the instrument
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Can verify image reconstruction from calunit
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Observations of the edges of the slitlets
Observations of the arc lines
Or spatial offsets measured from a star
KMOS IST meeting, ESO, 10tth May 2006
Data pipeline
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Philosophy
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Bringing in SINFONI experience
Minimise interpolations
Single set of routines for Quick-look, on-line
pipeline, off-line pipeline
IFU is the ‘unit’ of reduction
KMOS IST meeting, ESO, 10tth May 2006
Data pipeline
KMOS IST meeting, ESO, 10tth May 2006
Data pipeline: OH sky subtraction
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Discussed to be added
Scaling OH lines, in particular
KMOS IST meeting, ESO, 10tth May 2006
Data pipeline: OH sky subtraction
KMOS IST meeting, ESO, 10tth May 2006
Summary Science Requirements
Requirement
Essential
Requirements
PDR Prediction
Throughput
( REQ 3.5.1)
J>20%, H>30%, K>30%
J>30%, H>35%, K>35%
Wavelength
coverage
(REQ 3.5.5)
1.05 to 2.5 μm
0.8 to 2.5mm
Spectral
Resolution
(REQ 3.5.19)
R>3200,3800,3000 (J,H,K)
R=3500,3900,3700
Number of IFUs
(REQ 3.5.14)
24
24
Extent of each IFU
(REQ 3.5.10)
2.8 x 2.8 sq. arc seconds
2.8 x 2.8 sq. arc seconds
Spatial Sampling
(REQ 3.5.11)
0.2 arc seconds
0.2 arc seconds
Patrol field
(REQ 3.5.9)
5’x 5’ field
7.2 arcmin diameter field
Close packing of
IFUs
(REQ 3.5.15)
≥3 within 1 sq arcmin
≥3 within 1 sq arcmin
Closest approach
of IFUs (REQ
3.5.16)
2 target fields separated
by 6 arcsec
2 target fields separated by
6 arcsec, plus the ability to
assemble 24 IFUs into map
configuration
KMOS IST meeting, ESO, 10tth May 2006
IZ grating trade-offs
Performance gains
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KMOS offers high
throughput at
l>0.8um
Low background
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OH lines an order of
magnitude fainter
than JHK
At R=3500, 85% of
band free of lines
KMOS IST meeting, ESO, 10tth May 2006
Performance, R=3500
KMOS IST meeting, ESO, 10tth May 2006
Comparison with existing facilities
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In future, X-shooter with R~4-7000 single IFU
KMOS IST meeting, ESO, 10tth May 2006
Technical issues
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Coatings and optics
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Philosophy is to take what we get
Optimised for JHK, perform well at IZ
For IZ we require:
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One additional grating - selected
One additional blocking filter - selected
KMOS IST meeting, ESO, 10tth May 2006
Technical issues
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Grating turret
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Can accommodate 3 additional gratings
Does not increase in size
Weight limit still OK
IZ grating selected
Filter wheels
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Can accommodate the additional filter with
no change in size
Filter selected
KMOS IST meeting, ESO, 10tth May 2006
Resource issues
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Grating and filter will need installed,
tested and paid for
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3 x Z band gratings
3 x Z band filters
Alignment of filters
Alignments of gratings
Factory Calibrations etc
Total = £50K
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£
£
£
£
£
30K
8K
3K (0.05 FTE)
3K (0.05 FTE)
6K (0.1 FTE)
Additional time required in testing
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~1 month
KMOS IST meeting, ESO, 10tth May 2006