Instrument Science Report OSG-FGS-35
FGS Cycle 5 Calibration Closure
Sherie T. Holfeltz, Olivia L. Lupie, Lauretta M. Nagel
January 23, 1997
ABSTRACT
This document describes the current status of the Cycle 5 calibrations of the Fine Guidance Sensor #3. The calibrations for TRANSfer mode are complete and were documented
in earlier Reports. The POSition mode calibrations are still being reduced and will be presented in future ISRs.
Introduction
This report serves to document the current status of the Cycle 5 calibration program
for FGS #3. Tables summarizing both the planned and executed calibrations are given followed by detailed descriptions of the design and outcome of each program. Lessons
learned as a result of the Cycle 5 calibration plan which may prove useful for future calibration efforts are also discussed.
Summary of Cycle 5 Plan
The Cycle 5 Calibration plan for FGS #3 consisted of 6 programs (3 TRANSfer mode
and 3 POSition mode) with a combined total of 32 orbits. The program IDs, titles, frequency of execution, the number of orbits required, the human resources required, the
expected data products, desired accuracy and relevant notes are given for each program in
Table 1.
Summary of Cycle 5 Calibrations
The results to date of the Cycle 5 calibrations are summarized in Table 2. The program
IDs, titles, the number of orbits used, the human resources used, the generated data products made, the accuracy achieved and pertinent notes are given for each program.
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Table 1. FGS Cycle 5 Calibration Plan
Estimated Time (orbits)
ID
Proposal Title
Frequency
“External”
“Internal”
Required
Resources
(FTE)a
Products
Accuracy
Notes
Routine Monitoring Programs
6174
Delta Mini OFAD
1
11
0
0.02
PDB,
Pipeline
1.0-1.5
masb
Data to be reduced by STAT
6325,
6326
Long Term Stability Test
9
9
0
0.02
PDB,
Pipeline
3 mas/
axisb
Data to be reduced by STAT
6177
Intermediate Plate Scale
3
3
0
0.13
ISR,
Pipeline
6175
3 Points of Light
1
3
0
0.08
ISR,
Ref files
S/N > 100 Get ref. TFs (B-V=0.5) for F583W, PUPIL,
ISR,
Ref files
S/N > 100 Get ref. TFs (ref & blue stars) for F583W,
ISR,
Ref files
S/N > 100 Get ref. TFs (red & blue stars) for F5ND
0.5 mas/ Monitor plate scale in FGS #3
arc-minb
F5ND filters at 3 different positions in fov.
Special Calibration Programs
6180
6181
Red/Blue Transfer Functions
Red/Blue ND Transfer Functions
TOTAL TIME (including all executions)
1
1
3
3
32
NOTES:
aRequired Resources does not include modeling or extensive analysis.
bAssumes availability of STAT support.
0
0
0
0.04
0.04
PUPIL filters at central position in fov.
filter at central position in fov.
Table 2. FGS Cycle 6 Calibration Closure
Time Used (orbits)
ID
Proposal Title
“External”
“Internal”
Resources
Used
(FTE)
Products
Database Document
Accuracy
Achieved
Notes
Routine Monitoring Programs
6174
Delta Mini OFAD
11
0
0.02
Pipeline
TBD
TBD
Data reduced by STAT
6325,
6326
Long Term Stability Test
8
0
0.02
Pipeline
TBD
TBD
Data reduced by STAT
6177
Intermediate Plate Scale
3
0
0.15
Pipeline
TBD
TBD
Work in Progress by STAT
6175
3 Points of Light
3
0
0.1
Ref files
ISR #32
S/N > 100 S/N~ 30 for F5ND;
S/N ~ 100 for PUPIL & F583W
Special Calibration Programs
6180
6181
Red/Blue Transfer Functions
Red/Blue ND Transfer Functions
3
3
0
0
0.08
0.08
Ref files
Ref files
ISRs #31,
#31-Add.
S/N > 90 S/N > 100 (Red),
ISR #31
S/N > 90 S/N > 100 (Red),
S/N ~ 100 (Blue)
S/N ~ 100 (Blue)
TOTAL TIME (including all executions)
31
0
Details of Cycle 5 Calibration Programs
The plan for and results of each program are discussed below.
Details of the planned calibration are presented as follows. The purpose of each program is given followed by a description of the planned observations. The fraction of GO
and GTO programs supported by each calibration is noted. The planned number of orbits
and an estimate of the human resources required (Full Time Equivalent) to reduce and
document the data, perform trending analysis, etc. is given. Anticipated special requirements are listed, followed by the expected accuracy of the calibration and the projected
data products.
The results of each program are then discussed. First, any modifications which were
made to the program are listed. Any problems encountered during execution of the program are described. The total number of orbits used and the human resources used to date
(Full Time Equivalent) are given. The accuracy achieved and the data products generated
are noted. Finally, the time-line for the observations, data reductions and documentation is
recounted and any plans to continue the calibration in future cycles are discussed.
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Proposal ID 6174: FGS Cycle 5: Delta Mini-OFAD
Plan
Purpose: The goal of this program is to calibrate the changes to the Optical Field Angle
Distortions (OFAD) of FGS #3.
Description: This proposal would observe many stars in M35 through the F583W filter
over 11 contiguous orbits in autumn. The STAT would use the data to obtain an updated
solution for the Optical Field Angle Distortion calibration. This calibration is necessary
for the reduction of all POS Mode observations.
This program builds on previous OFAD and Delta Mini-OFAD programs and is designed
to calibrate the changes to the OFAD in FGS #3 observed after the Servicing Mission. The
re-collimation of the secondary mirror during SMOV (and the 11 micron re-focus) rendered the previous OFAD solution obsolete. With the current OFAD solution, plate overlay residuals of 4 to 5 milli-arc seconds are typical while our error budget is only 3 milliarc seconds.
This calibration is essential for all POS Mode observations, including those designed to
search for planetary companions, parallax and Proper Motion studies. Approximately 50%
of Cycle 5 GO and 88% of Cycle 5 GTO programs require this calibration.
Fraction of GO/GTO Programs Supported: 50% GO, 88% GTO
Resources:
Observation: 11 contiguous orbits
Analysis: 0.02 FTE
Special Requirements: We require that these observations be performed at the requested
orientation.
Accuracy: This calibration should result in errors of less than 2 milli-arc seconds across
much of the field of view; the error budget is 3 milli-arc seconds.
Products: The new OFAD coefficients (and related parameters) will be delivered by the
STAT for use in the reduction of astrometry data.
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Results
Modifications: None.
Execution: The observations executed nominally on 1-2 December, 1995.
Resources Used:
Observation: 11 contiguous orbits
Analysis: 0.02 FTE
Accuracy Achieved: 2 mas RMS
Products: The Astrometry Team was responsible for the data reduction. The optical distortion coefficients obtained in this calibration were incorporated by the Team into their
POS Mode data reduction software. This software and accompanying documentation is to
be transferred to the STScI during Cycles 6 and 7.
Time-line: The observations executed over 11 contiguous orbits on 1-2 December, 1995.
The Astrometry Team’s POS Mode data reduction software, which uses the optical distortion coefficients obtained from this calibration program, is to be transferred to the STScI
during Cycles 6 and 7. Documentation should be available shortly thereafter.
Continuation Plan: There will be an operational (as opposed to scientific) Mini-OFAD
for each FGS performed during SMOV; these tests are designed to determine the optical
distortions to the level necessary to support spacecraft guidance. This data should be sufficient to assess whether or not the second servicing mission affected the optical distortion
to such an extent that another scientific OFAD calibration might be required.
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Proposal ID 6325 & 6326: FGS Cycle 5: Monitor the Long Term Stability of FGS #3
Plan
Purpose: The purpose of this program is to characterize and monitor the internal positional stability of FGS #3 and estimate and monitor the differential corrections to the
OFAD and Plate Scale calibrations.
Description: Several stars in M35 will be observed repeatedly throughout the year on a
roughly monthly basis. Up to 30 observations per visit, using the F583W filter, will be
made of targets in M35.
Fraction of GO/GTO Programs Supported: 50% GO, 88% GTO
Resources:
Observation: 8 orbits.
Analysis: 0.02 FTE.
Special Requirements: None.
Accuracy: 2.7 mas RSS
Products: OFAD and plate scale coefficients will be used in pipeline calibrations and data
reductions and for trend analysis.
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Results
Modifications: None.
Execution: Execution was nominal.
Resources Used:
Observation: 8 orbits.
Analysis: 0.02 FTE.
Accuracy Achieved: 2.7 mas RSS.
Products: The corrections to the OFAD and plate scale calibrations are incorporated by
the Astrometry Team into their data reduction software.
Time-line: The data were obtained in September, October and November of 1995, January, February, March and twice in April 1996. (The target goes behind the sun for 3
months in early May.)
Continuation Plan: This monitoring program must be continued. The data exhibit variations which are on the order of 1 mas over time scales of a month or less and do not follow
any perceptible trends.
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Proposal ID 6177: FGS Cycle 5: Intermediate Plate Scale
Plan
Purpose: The goal of this program is to refine our knowledge of the plate scale in the central region of the astrometer FGS.
Description: Short POSition Mode observations are to be made through the F583W filter
of an asterism observed expressly for this calibration by the ESA satellite HIPPARCOS
and astrometric reference stars. Up to 30 observations are to be made per orbit, including
several “check stars” which are each observed multiple times per orbit, to facilitate the
detection and removal of drift. There will be 3 observation sets over the cycle.
Fraction of GO/GTO Programs Supported: 50% GO, 88% GTO
Resources:
Observation: 1 orbit per visit, 3 visits per cycle = 3 orbits
Analysis: 0.13 FTE
Special Requirements: We require the observations to be made on or near the dates and
orientations specified.
Accuracy: The plate scale obtained should be accurate to < 0.5 milli-arc seconds per arc
minute.
Products: The data reduction will be discussed in an Instrument Science Report and the
plate scale should be available for use in data reduction no later than 6 weeks after the final
observations are made.
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Results
Modifications: After one visit with the PUPIL filter was executed, it was determined that
this filter would be removed from the Intermediate Plate Scale calibration program. The
plate scale calibration requires an OFAD correction; the OFAD is only calibrated for the
F583W filter.
Execution: This program executed nominally.
Resources Used:
Observation: 4 orbits.
Analysis: 0.15 FTE
Accuracy Achieved: Work in progress.
Products: The plate scale is to be included in the PDB and CDBS and will be used in the
POS Mode data reduction software.
Time-line: The data were obtained on 17 & 19 July 1995, 7 January 1996 and 5 February
1996. The data were given to the STAT in October 1996 after the HIPPARCOS positions
for the calibration targets were obtained. A relative scale solution is expected by 31
December 1996; an absolute scale should be calculated in early 1997 and will be presented in an ISR.
Continuation Plan: The Intermediate Plate Scale should continue to be monitored at least
through Cycle 7 since other calibration programs (e.g., Mini-OFAD and Long Term Stability) cannot separate an absolute overall scale term from other parameters (such as the
lever arm lengths).
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Proposal ID 6175: FGS Cycle 5: Three Points of Light
Plan
Purpose: This program provides reference Transfer Functions for the FGS standard star
Upgren 69 (B-V = 0.5) using the F583W, PUPIL, and F5ND filters at three positions in the
field of view.
Description: Reference Transfer Functions for use in the reduction of TRANS Mode data
will be obtained at three positions distributed azimuthally along the midline of the field of
view. The F583W, PUPIL, and F5ND filters will be used.
Fraction of GO/GTO Programs Supported: 83% GO, 24% GTO.
Resources:
Observation: 3 orbits.
Analysis: 0.08 FTE.
Special Requirements: None.
Accuracy: The signal to noise ratio should be greater than 100; this may not be attained
for the Neutral Density filter.
Products: The reference Transfer Functions will be presented in an Instrument Science
Report and should be available for use in data reduction no later than 4 weeks after the
observations are complete.
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Results
Modifications: None.
Execution: This program executed without any problems.
Resources Used:
Observation: 3 orbits.
Analysis: 0.1 FTE
Accuracy Achieved: The S/N obtained for the PUPIL and F583W filters ranged from 90
to 170. The S/N obtained for the F5ND filter was approximately 30. Here, S/N is defined
as the peak-to-peak amplitude of the Transfer Function divided by the standard deviation
of the Transfer Function far ( > 300 milli-arc seconds) from the null.
Products: The reference Transfer Functions are stored in an on-line library for use in data
reductions. Trending studies are ongoing and will be summarized in a future ISR.
Time-line: The observations occurred between 11-16 September 1995. The ISR (#32) was
issued on 20 September 1995. Trending studies are continuing.
Continuation Plan: This monitoring of the TF must continue. Changes in the TF (on the
order of 5-10%) have been observed and need to be characterized and monitored. Trending studies are continuing.
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Proposal ID 6180: FGS Cycle 5: Red/Blue Transfer Function Calibration
Plan
Purpose: This program provides reference Transfer Functions using the F583W and
PUPIL filters at the center of the field of view. The targets have B-V = 0.18, 1.35, and
1.92.
Description: Reference Transfer Functions for use in the reduction of TRANS Mode data
will be obtained at the center of the field of view. The F583W and PUPIL filters will be
used.
Fraction of GO/GTO Programs Supported: 83% GO, 35% GTO
Resources:
Observation: 3 orbit.
Analysis: 0.04 FTE
Special Requirements: None.
Accuracy: The S/N should be > 100.
Products: The reference Transfer Functions will be presented in an Instrument Science
Report and should be available for use in data reduction no later than 2 weeks after the
final observations are complete.
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Results
Modifications: None.
Execution: One visit, to observe the LAT-COL-1B target with the F583W and PUPIL filters, failed. The visit was rescheduled and executed successfully. The remaining visits executed nominally.
Resources Used:
Observation: 3 orbits.
Analysis: 0.08 FTE.
Accuracy Achieved: The S/N obtained exceeded the stated requirements.
Products: The Transfer Functions and their assessments were presented in ISR #31 and
ISR #31-Addendum. The reduced data files were included in the on-line library of reference files to be used in the reduction of calibration, GO and GTO TRANS Mode observations. The results of ongoing trending studies will be presented in a future ISR.
Time-line: Two visits were executed on 6 September 1995. The data from these observations was reduced and documented in ISR #31 which was released on 25 September 1995.
The remaining visit executed on 9 January 1996; the corresponding report, ISR #31Addendum, was issued on 17 January 1996. The reference files were made available for
use in data reductions immediately prior to the distribution of the related ISR.
Continuation Plan: This calibration must be continued and possible expanded (if suitable
targets can be identified). The affect of the color index of the target on the morphology of
the observed Transfer Function is non-negligible. Currently, the calibration must continue
because until the Institute has a working model with which one may synthesize a reference
Transfer Function of the desired color, observers are limited to the finite grid of targets and
filters in the current calibration plan. In the future, if a successful “longitudinal color”
model is developed, one would likely interpolate between these calibration scans to model
the response to a target of a given color index. Trending studies also continue.
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Proposal ID 6181: FGS Cycle 5: Red/Blue ND Transfer Function Calibration
Plan
Purpose: This program provides reference Transfer Functions using the F5ND filter at the
center of the field of view. The targets have B-V = -0.1, 1.28 and 1.7.
Description: Reference Transfer Functions for use in the reduction of TRANS Mode data
will be obtained at the center of the field of view. The F5ND filter will be used.
The shape of an observed Transfer Function depends on such factors as the color index of
the target, the filter used and the position in the field of view. TRANS Mode data reduction
involves comparing the observed data to the appropriate reference data, i.e., the observed
and reference data must have been taken on targets of comparable color index near the
same position in the field of view with the same filter. This calibration is necessary for all
TRANS Mode programs, including those involving double stars, which contain targets of
extreme color index and use either the F5ND filter. Approximately 42% of the Cycle 5 GO
programs and 6% of the Cycle 5 GTO programs require this calibration
Fraction of GO/GTO Programs Supported: 42% GO, 6% GTO
Resources:
Observation: 3 orbits
Analysis: 0.04 FTE.
Special Requirements: None.
Accuracy: S/N should be greater than 100.
Products: The reference Transfer Functions will be presented in an Instrument Science
Report and should be available for use in data reduction no later than 2 weeks after the
final observations are complete.
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Results
Modifications: No modifications were made to the Cycle 5 program. However, the probable duplicity of one of the calibration targets, HD 28149, was discovered after the data
were obtained. A new target, HD 89309 (a.k.a. SAO 118211) with a B-V color index of
0.05, was chosen as a replacement for Cycles 6 and beyond.
Execution: The observations executed nominally.
Resources Used:
Observation: 3 orbits.
Analysis: 0.08 FTE.
Accuracy Achieved: The S/N obtained exceeded the stated requirement.
Products: The Transfer Functions and their assessments were presented in ISR #31. The
reduced data files were included in the on-line library of reference files to be used in the
reduction of calibration, GO and GTO TRANS Mode observations. The results of ongoing
trending studies will be presented in a future ISR.
Time-line: The observations were executed between 15 - 17 September 1995. The data
were reduced, assessed and documented and ISR #31 was issued on 25 September 1995.
The reference files were made available for use in data reductions by 18 September 1995.
Continuation Plan: This calibration must be continued and possible expanded (if suitable
targets can be identified). The affect of the color index of the target on the morphology of
the observed Transfer Function is non-negligible. Currently, the calibration must continue
because until the Institute has a working model with which one may synthesize a reference
Transfer Function of the desired color, observers are limited to the finite grid of targets and
filters in the current calibration plan. In the future, if a successful “longitudinal color”
model is developed, one would likely interpolate between these calibration scans to model
the response to a target of a given color index. Trending studies are continuing.
16