Technical Instrument Report WFPC2 2002-007
The WFPC2 Photometric
Monitor
S. Gonzaga, C. Ritchie, S. Baggett, B. Whitmore, and S. Casertano
December 24, 2002
ABSTRACT
This report documents the standard WFPC2 photometric monitor software package, and
associated scripts for generating plots and creating the photometric monitor memorandum that is regularly updated on the WFPC2 website. Also included are some general
plots of photometric monitor trends for the primary photometric filters, from May 1, 1994
to June 17, 2002.
Introduction
Since the installation of WFPC2 in late 1993, most photometric calibration and monitor efforts have been done using observations of the WFPC2 standard star
GRW+70D5824, a high proper motion white dwarf of spectral class DA3, with V=12.77
and B-V=-0.09. The observations described in this document were used for monitoring
system throughputs and contamination rates, updating zeropoints, and checking instrument focus.
This star has been consistently observed since the instrument was activated in 1993,
but we will only consider data starting from May 1, 1994 because the operating temperature of the instrument was lowered from -77C to -88C in April of 1994 to improve the
charge transfer efficiency. Observations have been typically conducted once or twice a
month, using most of WFPC2’s primary photometric filters: F336W, F439W, F555W,
F814W, and occasionally F300W and F675W. Additional observations using UV filters -F160BW, F170W, F218W, and F255W -- have been used to monitor UV throughput
before and after decontaminations. A list of all photometric monitor programs can be
found in table 1.
Copyright© 2002 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.
Technical Instrument Report WFPC2 2002-007
Prop. ID
Type
Time Interval
Chip
Filters
5563
Calibration
1994-05-01 to 1995-02-13
PC
F160BW, F170W, F218W,
F255W, F336W, F439W,
F555W, F675W, F814W
5629
Calibration
1994-04-25 to 1995-07-26
All chips
F170W
6143
Calibration
1995-03-07 to 1995-07-06
PC
Same as 5563
6184
Calibration
1995-07-27 to 1996-06-06
Alternating
chips for each
decon cycle
Same as 5563
6902
Calibration
1996-07-27 to 1997-07-25
Same as 6184
Same as 5563
7211
pre-SM2
1996-11-15
PC
F170W, F555W, F160BW
7016
SM2
1997-03-24 to 1997-04-07
All chips
F555W, F170W
7618
Calibration
1997-07-22 to 1999-04-25
Same as 6184,
pre-decon
obs. done
every other
decon
Same as 5563
7925
post-NIC3 campaign
focus verification
1998-02-02
PC
F555W
8441
Calibration
1999-05-02 to 1999-08-11
Same as 7618
Same as 5563
8491
SM3A
2000-01-16 to 2000-01-31
All chips
F555W, F170W
8459
Calibration
2000-04-17 to 2000-07-15
Same as 7618
Same as 5563
8822
Calibration
2000-08-07 to 2000-09-10
Same as 7618
Same as 5563
8893
Shutter RAM Patch
Test
2000-11-10
Same as 7618
Same as 5563
8823
Calibration
2000-11-29 to 2001-03-07
Same as 7618
Same as 5563
8824
Calibration
2001-03-19 to 2001-05-17
Same as 7618
Same as 5563
8825
Calibration
2001-07-14 to 2001-09-09
Same as 7618
Same as 5563
8932
Calibration
2001-11-01 to 2002-01-26
Same as 7618
Same as 5563
8943
pre-SM3B
2001-12-01
PC,WF2,
WF3
F170W, F555W, F160BW
8950
post-SM3B
2002-03-23 to 2002-04-06
All chips
Same as 5563, but no
F160BW
8953
post-SM3B
2002-03-31
All chips
Same as 5563
8933
Calibration
2002-02-23 to 2002-05-18
Same as 7618
Same as 5563
8934
Calibration
2002-06-11 to present
Same as 7618
Same as 5563
Table 1: Photometric Monitor Programs for WFPC2. Only data from calibration programs were
used for the results presented in this document. (Note: there were no pre-SM3A observations of
GRW+70D56824.)
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Technical Instrument Report WFPC2 2002-007
Photometry-related WFPC2 History
When WFPC2 first became operational, the instrument’s operating temperature was
-77C, selected to keep the accumulation of contaminants on the CCD window as low as
possible, while keeping the dark noise at an acceptable value. However, this operating
temperature resulted in relatively low charge transfer efficiency (CTE) due to low-level
traps in the CCDs (about 10% from top to bottom of chip). As a result, the instrument temperature was lowered to -88C on 23 April, 1994, where it remains today. This lower
operating temperature reduced charge transfer inefficiency (CTI) to about 4% at that time
but resulted in higher contamination rates, making it necessary to decontaminate the CCD
windows by heating them to +22C every 28 days.
Normal decontaminations proceed as follows:
1. The shutter is open, and there is no filter in place.1
2. Thermoelectric coolers are turned off.
3. CCD heaters are turned on to preheat the detectors. It slowly reaches about -40C
(over the course of an hour) in order to minimize thermal impact to the CCDs.
4.
Heatpipe heaters turned on.
5. Within 1.5 hour, the CCDs reach +22C, and are maintained at that temperature for
at least 6 hours.
6. Heatpipe heaters turned off, and thermoelectric coolers turned on.
7. After about 15 to 30 minutes, CCD heaters are turned off, and detectors are cooled
to -88C (which takes about 2.5 hours).
Past analyses of UV photometric monitor data have indicated that the contamination
rates appear to be decreasing with time (ISRs 98-03, 97-10, 96-07, and 96-02, as well as
more recent analysis by McMaster and Whitmore in ISR 02-07: Updated Contamination
Rates for WFPC2 UV Filters). That decrease, combined with the reduction in WFPC2 use
for cycle 11 (beyond July 2002) led to the decision by the WFPC2 group at STScI to
increase the interval of time between contaminations from 28 days to 49 days.
In addition to the regular monthly decons, there have been several events that could
have potentially affected WFPC2 throughput, and the photometric monitors were used to
verify that the instrument was functioning normally. Listed below are major events.
1
For “special decontaminations” performed during Servicing Mission Orbital Verification programs,
the shutter is closed and the F785LP filter is put in-place to help keep contaminants from entering the
camera.
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Technical Instrument Report WFPC2 2002-007
•
The NIC-3 campaigns: The three NICMOS cameras were originally designed to be
parfocal. But due to dewar problems caused by thermal stresses before launch and a
deformation after launch, the NIC3 camera focus was pushed outside the range of its
internal focusing mechanisms. Because of this problem, and a shortened dewar lifetime (due to a faster coolant rate dissipation by a thermal short caused by the dewar
deformation), two NIC3 campaigns were scheduled to take advantage of this unique
IR mode before the instrument ran out of coolant. To do this, the HST secondary mirror was moved to provide in-focus images in NIC3 (causing out-of-focus images in the
other instruments). The first campaign occurred from January 12 to February 1, 1998.
During this time, no WFPC2 images were taken except for standard darks and internal
monitors. At the end of the campaign and after the secondary mirror had been moved
to its nominal position, WFPC2 observations were used to verify focus (program
7925).
The second NIC3 campaign took place from the 4th to 28th of June. During this time,
four long decontaminations were done early in the campaign -- the CCDs were heated
to +22C for 24 hours for each decontamination (program 8049). Besides standard
darks and internal monitors, observations were taken of GRW+70D5824 (program
7618) while WFPC2 was out-of-focus to create calibration PSFs for parallel WFPC2
observations taken with the NIC3 Hubble Deep Field program (program 7817). After a
regular decontamination, and return of the secondary mirror to its nominal position, a
visit in calibration program 7618 was used to verify WFPC2 focus.
•
Shutter Ram Patch: From August to October of 2000, a number of WFPC2 observations failed due to a problem with the shutter. A LED/phototransistor, used by the
flight software to sense shutter A’s position before commanding it to open, was not
working correctly, causing the software to become confused and close the shutter. As
concerns about damage to the shutter mechanisms mounted, in October, a decision
was made to intentionally put WFPC2 in safemode until the problem was resolved
with a software patch. This was done on November 1, 2000, and no shutter problems
have been reported since.
•
November 13, 1999 (1999.317): HST entered zero gyro mode at 13:29:39 due to the
failure of one of three remaining operating gyros. No observations were possible until
after Servicing Mission 3A that ended on Christmas day of 1999. Science observations
with WFPC2 resumed on January 11, 2000 following a decontamination and photometric monitor that indicated that the instrument was performing well.
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Technical Instrument Report WFPC2 2002-007
•
August 5, 2000: HST entered PSEA (Pointing/ Safemode Electronics Assembly) Sunpoint Safemode, resulting in some equipment, including WFPC2, being turned off.
This caused WFPC2 to warm to -40C (from -88C) for about a day. At the time of the
safing, more than 3 weeks had elapsed since the last decontamination. After WFPC2
was brought back into operation at the usual -88C temperature, on August 6th, photometric monitor data indicated that the -40C warm-up had acted like a decontamination.
UV throughput had increased to levels typically seen shortly after a decontamination.
Also, some moderate annealing of hot pixels had occurred. Users who obtained data
between August 6 and August 10th, 2002 (the next decontamination date), were
advised to make their UV throughput corrections assuming an August 6th decontamination.
•
March 7th, 2001: A spacecraft safing (due to magnetic torquing bars being out of limits) occurred, causing the instrument to be warmed to -40C. No decontamination was
performed after recovery (on March 7, 2001, 05:00:57.60 UT), and subsequent UV
photometric observations of GRW+70D5824 produced the nominal post-decontamination results.
•
A non-standard decontamination occurred on November 30, 2001. The WFPC2 was in
the decontamination state for 28 hours because of special activities: the retraction of
COSTAR and a NSSC-1 software upgrade. UV Photometric monitor observations
after that event showed nominal post-decon results.
WFPC2 photometric monitoring was also undertaken during the Servicing Mission
Orbital Verification Periods2 (SMOV) that followed each servicing mission. After the
instrument was brought out of the “protect” state, it underwent what’s called a “special
decontamination.” These are just like regular decontaminations except the shutter is closed
and the F785LP filter is put in place to keep possible contaminants from entering the
instrument. Also, in protect decontaminations, the period of time that the instrument is
maintained at +22C is longer, for instance, for 9 hours during SMOV3B. After a special
decontamination, frequent observations of a standard star were taken with the F170W filter to check contamination conditions. Data from SMOVs are not included in this
document because of higher contamination on the CCD window compared to nominal
operating conditions. More information about SMOV photometric monitors, for SM2,
SM3A, and SM3B, can be found in Instrument Science Reports listed at http://
www.stsci.edu/instruments/wfpc2/wfpc2_bib.html.
2 Table
2: Servicing Mission (SM) and WFPC2 Servicing Mission Observatory Verification Dates.
SM#
SM Dates
WFPC2 SMOV Dates
2
Feb. 13-19 ‘97
Feb. 23 - Apr. 05 ‘97
3A
Dec. 19-25 ‘99
Dec.25 ‘99 - Feb 01 ‘00
3B
Mar. 3-9 ‘02
Mar. 12 - Apr. 19 ‘02
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Technical Instrument Report WFPC2 2002-007
Data Analysis and Results
All photometric monitor data is processed in the standard WFPC2 pipeline, using
calwp2. The steps for basic data reduction and dissemination of photometric monitor data
are as follows:
1. Countrates and data quality checks of the standard star are obtained using an IRAF
package called photscr. (This package was originally written by Christine Ritchie,
and has since undergone some modifications by the first author.) Procedures for
reducing the data using the photscr package can be found in appendix A.
The noao.digiphot.apphot.phot task is used to obtain the counts. Major parameter settings are:
•
Aperture radius of 5 pixels for WF chips and 11 pixels for the PC chip.
•
Inner sky annulus radius of 15 pixels with radius width of 5 pixels for the WF chips.
For the PC, those same values are 32 and 11 pixels, respectively.
•
The sky-fitting algorithm is ofilter. This method is selected based on recommendations
in WFPC2 ISR 96-03: Background Subtraction in WFPC2 Frames.
2. The igi scripts for plotting the countrates (also originally written by Christine
Ritchie, with some later modifications by the first author) creates a summary of
countrates in all regularly-monitored filters, from May 1, 1994 to June 17, 2002,
showing long-term trends in throughput (see figure 2). The UV filters each have
two nearly parallel sets of points: the higher points were taken immediately after a
decon, the lower throughput points taken just before a decon. Instruction on how to
create plots are found in Appendix B.
Figure 1: GRW+70D5824 in the PC/F555W configuration.
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Technical Instrument Report WFPC2 2002-007
Figure 2: Photometric throughput in the WFPC2 primary filters of standard star
GRW+70D5824, from May 1, 1994 to June 17, 2002. This particular plot was
created on July 5th, 2002, and will continue to be regularly updated on the
WFPC2 webpage.
3. The results of the photometric monitor are regularly posted to the WFPC2
webpage. A series of simple IRAF scripts are used to format the data for the online photometric monitor memo (see appendix C). This memo and database are
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Technical Instrument Report WFPC2 2002-007
continually updated with the results from the most recent observations. The database contains the following columns:
Column Name
propid
obsmode
Definition
Proposal number of calibration program.
Observing mode parameters: instrument, chip, gain, and filter.
ctrate 3
Actual countrate (DN/s) for the 0.5" radius aperture. (All observations taken
at gain 15.)
Measurement uncertainty of the countrate.
Normalized countrate, normalized to noted reference observations.
Measurement uncertainty for the normalized countrate.
Date of observation.
Modified Julian Date (Julian Date - 2400000.5) for the observation.
Exposure time of observation
Number of days since the prior decontamination for each
observation.
ctr_err
norm_ctr
norm_err
date
mjd
exptime
dsd
The latest version of this memo can be accessed at http://www.stsci.edu/instruments/
wfpc2/Wfpc2_memos/wfpc2_stdstar_phot3.html (Note: Data taken at -77C and for serials=ON have been excluded from the photometric monitor database.)
The photometric monitor data have been used to monitor trends in the data. Figures
3a-3i show the general photometry trend (normalized countrates vs. Modified Julian Date)
for each primary photometric filter/chip combination from May 1994 to June 2002. Figures 4a-4f show the changes in contamination rate with time (normalized throughputs vs.
days since decontamination) for UV filter data in the PC and WFC3.
3
Note that the countrates have intentionally not been corrected for secondary effects such as long vs.
short, CTE, aperture correction, etc..
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Technical Instrument Report WFPC2 2002-007
Figure 3a. F160BW Throughput vs. MJD in PC, WF2, WF3, and WF4.
9
Technical Instrument Report WFPC2 2002-007
Figure 3b. F170W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3c. F218W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3d. F255W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3e. F336W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3f. F439W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3g. F555W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3h. F675W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 3i. F814W Throughput vs. MJD in PC, WF2, WF3, and WF4.
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Technical Instrument Report WFPC2 2002-007
Figure 4a. F160BW PC and WF3 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Figure 4b. F170W PC and WF3 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Figure 4c. F170W WF2 and WF4 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Figure 4d. F218W PC and WF3 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Figure 4e. F255W PC and WF3 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Figure 4f. F336W PC and WF3 Throughput Decline vs. Days Since Decontamination.
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Technical Instrument Report WFPC2 2002-007
Conclusions
•
Plots in figures 3a and 3b show an increase in post-decontamination throughput over
time for PC observations using F160BW and F170W filters. The F170W/PC, in particular, presents an interesting case: the throughput trend shows an increase, presumaby
because of a gradual outgassing of contaminants, followed by a levelling-off starting
around MJD 51600 (February 2000). This levelling-off could be due to worsening
CTE effects “pulling down” the increasing throughput trend (Whitmore, private communication). F218W and F255W show a decrease in post-decontamination throughput, while F170W WF chips appear stable. There is no obvious trend in F336W.
•
For filters F218W, F255W, F336W, F439W, F555W and F814W (figures 3c - 3i), there
is a noticeable decrease in throughput over time, most likely due to worsening CTE
effects. A more thorough analysis of this phenomena can be found in Technical Instrument Report WFPC2-02-04: SMOV3B WFPC2 Photometry Check (Whitmore &
Heyer), and will also be available in an Instrument Science Report about WFPC2
SMOV3B analysis, currently in preparation. Measurements of the throughput decline
vs. time for the above-mentioned filters, in the PC and WFC3, can be found in table 3.
•
There is a noticeable jump in throughput from MJD 49473 to 49900 (early May 1994
to early July 1995) seen in througput plots for F439W/PC, F439W/WF3, F555W/
WF3, F675/PC, F675W/WF3, F814W/PC, and F814W/WF3 (figures 3f to 3i). The
reason for this is currently unknown. (Note: Data from the early part of the postcooldown period (program 5563) had shorter exposure times. However, there is no evidence for non-linear countrates because the counts that show this “jump”s include
observations taken with longer exposure times.)
•
The plots for UV filters F160BW, F218W, F255W, and F336W, as seen in figures 4a,
4c-4f shows that the contamination rates have decreased over time, except in the case
of F170W (figure 4b) where WF post-decon throughputs have remained remarkably
similar from May 1994 to the present. A requirement for WFPC2 UV observations is
that throughput due to contamination should never drop below 70% of the total (postdecon) throughput. To meet this requirement, the intervals between decontaminations
in previous cycle were set at 28 days. But with the decreased contamination rates seen
in data over the past two year, in conjunction with anticipated decline in WFPC2 use
(due to ACS availability), the WFPC2 group decided it was safe to increase the interval between decontaminations to 49 days, starting in July 2002 (cycle 11). In addition,
updated contamination corrections are being generated so that users can correct the
photometry of their UV observations. These results will be released shortly in an ISR
(McMaster and Whitmore, in prep).
24
Technical Instrument Report WFPC2 2002-007
Table 3. A linear fit was applied to the data in figures 3c-i, for PC and WF3 only, in the form of
y = a + bx. The table below provides the values for a and b, the percentage decline in throughput from MJD 49900 to 52400 (early July 1995 to early May 2002, all data taken at -88C), and
its uncertainty. This range of dates was selected to exclude the “jump” seen prior to
MJD 49900. UV Filter/Chip entries marked with a * indicates that the linear fit was done using
data that was taken within 7 days before a decon, to reduce uncertainties due to contamination.
Filter/Chip
a
b
Sigma
Throughput
Decline (%)
Jul ‘95-May ‘02
Uncertainty
(+/- %)
F218W/PC*
1.8202591
-1.6460205E-5
5.95739100E-6
-4.115051
1.489348
F218W/WF3*
1.2857069
-6.8561269E-6
6.18179100E-6
-1.714032
1.545448
F255W/PC*
2.3127509
-2.6656047E-5
4.43048100E-6
-6.664012
1.10762
F255W/WF3*
2.2954517
-2.5973184E-5
1.06759300E-5
-6.493296
2.668983
F336W/PC*
1.9819521
-1.8953647E-5
3.44245600E-6
-4.738412
0.860614
F336W/WF3*
2.1975391
-2.3596809E-5
3.86018600E-6
-5.899202
0.9650465
F439W/PC*
1.8526549
-1.6487107E-5
2.64845500E-6
-4.121777
0.6621137
F439W/WF3*
1.6626646
-1.2592983E-5
4.66329300E-6
-3.148246
1.165823
F555W/PC
1.586595
-1.1620268E-5
1.09167400E-6
-2.905067
0.2729185
F555W/WF3
1.4628709
-9.201378E-6
2.67086400E-6
-2.300344
0.667716
F675W/PC
1.6588454
-1.2746172E-5
1.94079000E-6
-3.186543
0.4851975
F675W/WF3
1.4722014
-9.5245451E-6
3.32226600E-6
-2.381136
0.8305665
F814W/PC
1.7580882
-1.4433601E-5
1.66615900E-6
-3.6084
0.4165398
F814W/WF3
1.5867401
-1.104078E-5
2.44480200E-6
-2.760195
0.6112005
Acknowledgements
The authors wish to thank the following people for their contributions:
Jesus Balleza
Vicki Balzano
John Biretta
Mark Clampin
Harry Ferguson
Inge Heyer
J. C. Hsu
Anton Koekemoe
Lori Lubin
John MacKenty
Matt McMaster
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Technical Instrument Report WFPC2 2002-007
Max Mutchler
References
STANDARD STAR MONITORING MEMO
http://www.stsci.edu/instruments/wfpc2/Wfpc2_memos/wfpc2_stdstar_phot3.html,
Gonzaga et. al.
WFPC2 HISTORY FILE
http://www.stsci.edu/instruments/wfpc2/Wfpc2_memos/wfpc2_history.html, Baggett et.
al.
WFPC2 INSTRUMENT HANDBOOK:
http://www.stsci.edu/instruments/wfpc2/Wfpc2_hand/wfpc2_handbook.html, ed. Baggett
& McMaster
TIR WFPC2-02-04: SMOV3B WFPC2 Photometry Check, Whitmore & Heyer
http://www.stsci.edu/instrument-news/INTERNAL/wfpc2_tir.html
ISR WFPC2 98-03: WFPC2 Long-Term Photometric Stability
http://www.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr9803.html, Baggett &
Gonzaga
ISR WFPC2 96-03: Background Subtraction in WFPC2 Frames
http://www.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr9603.html, Ferguson
ISR WFPC2 96-02: Contamination Correction in SYNPHOT for WFPC2 and WF/PC-1
http://www.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr9602.html
ISR WFPC2 96-07: WFPC2 Throughput Stability in the Extreme Ultraviolet (abstract),
PostScript (0.12 MB) - MacKenty and Baggett.
http://www.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr9607.html
ISR WFPC2 97-10: WFPC2 SYNPHOT Update
http://www.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr9710.html
26
Technical Instrument Report WFPC2 2002-007
APPENDIX A
Procedure for Reducing WFPC2 Photometric Monitor Data
NOTE for SMOV Data Reductions:
“Quicklook” data is data processed immediately after POD files sent from PACOR
(PACket processOR at Goddard). After preliminary processing, the data is FTP’d to a
machine for retrieval by the science groups. This quicklook data is usually in the form of
Extension Fits Files, not the waivered FITS files normally used for WFPC2 data.
1. If you receive data in extension FITS format, it can easily be converted to GEIS by
using fits2geis (located at /usr/stsci/stlocal/bin.ssun/fits2geis.e). This task needs to
be run from the UNIX command line, not from IRAF.
Example:
/usr/stsci/stlocal/bin.ssun/fits2geis.e u6h41106m_c0f.fits
2. If you’re not sure if the data is extension FITS, here’s simple test:
The catfits routine can distinguish between extension FITS and waivered FITS files. In
the catfits results, waivered FITS files shows up with 3 dimensions (e.g., 800x800x4)
while extension FITS will have only 2 dimensions.
Example of running catfits on a waivered FITS file:
catfits u22p0106t_c0f.fits
EXT# FITSNAME
FILENAME
0
1
u22p0106t_c0f u22p0106t_cvt.c0h
TABLE
u22p0106t_cvt.c0h.tab
EXTVE DIMENS
800x800x4
49Fx4R
BITPI OBJECT
-32F
Example of running catfits with an extension FITS file:
catfits u22p0106t_c0f.fits
EXT# FITSNAME
FILENAME
0
1
2
3
4
EXTVE DIMENS
u22p0106t_c0f u22p0106t_c0f.fits
IMAGE
SCI
1 800x800
IMAGE
SCI
2 800x800
IMAGE
SCI
3 800x800
IMAGE
SCI
4 800x800
27
16
-32
-32
-32
-32
BITPI OBJECT
Technical Instrument Report WFPC2 2002-007
PROCEDURE FOR REDUCING WFPC2 STANDARD STAR PHOTOMETRIC
MONITOR DATA
Initial Set-up:
•
Put this in your loginuser.cl file.
task $photscr = “/data/wfpc14/PHOT_MON/photscr/photscr.cl”
This will allow you to run the tasks in the photscr package.
•
Load the following iraf packages:
noao digiphot apphot photscr
When photscr is loaded in IRAF, the following tasks are displayed:
checksat dochop dodophot dosep
getcounts runtvmark
chop
doctr
dosat
doseppartb runphot
tpsynlike
Notes:
•
the tasks dosep and doseppartb are from earlier versions of the package and are no
longer used.
•
Scripts for these tasks are archived at /data/wfpc14/PHOT_MON/
photmon_software_archive/photscr. The official version of the package code (which
should be pointed to in your loginuser.cl file) resides at /data/wfpc14/PHOT_MON/
photscr/.
A Summary of Steps
1a. Clear cosmic rays in the area around the stars.
1b. Create a coordinate list called “imcntr.out” containing the name of each image
and the position of the star.
2. Run the task runtvmark to verify that the positions in the “incntr.out” file
are correct.
3. Check for saturated pixels by running the checksat task
4. Trim the images to a smaller format using the dochop task
5. Run the photometry task using runphot.
6. Create a table of photometry results, using getcounts.
The Detailed Procedure
Note: The following procedure works only on single frames. If the standard star is in a
chip other than the PC, don’t forget to use the correct chip for the data quality checks.
Example where the standard star is in the WF2 chip of a 4-group image.
imcopy u5if3101r.c1h[2] i.c1h
imdel u5if3101r.c1h
imrename i.c1h u5if3101r.c1h
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Technical Instrument Report WFPC2 2002-007
1a. Using imedit, remove cosmic rays around the star. For the PC, clean a 40 pixel radius
around the star. For the WF, clean a 20 pixel radius around the star. Example:
imedit u5if3101r.c0h[2] i.c0h
imdel u5if3101r.c0h
imrename i.c0h u5if3101r.c0h
<--- remove the cosmic rays, when done, type “q” to quit
IMPORTANT: If a cosmic ray falls on a star, or is so close to the star that it cannot be
removed, do not use that star. Completely remove that image and data quality file from
the working directory -- this is needed to properly run the photometric monitor script.
For imedit novices: this is a versatile image editing task. After executing the imedit
command, the image is displayed on the image display tool (saoimage or ximtool), and
a cursor appears on the screen (cross for saoimage, blinking circle for ximtool). A few
of the commonly-used commands are listed below.
a
To do a background substitution of a large cosmic ray more than 2 pixels wide,
imagine a box around the cosmic ray. Place the cursor at one corner and type a.
You will be prompted to do it again (on the window where imexam was launched).
Put the cursor on the opposite corner and type a again.
b To do a background substitution on a small cosmic ray, you can use a pre-defined
circular aperture. Place the cursor on the cosmic ray and type b (The radius of the
circular aperture can be set using:radius [value].
q To quit and save your results, type q.
Q To quit and _not_ save your results, type Q.
When working in imedit, a list of commands can be displayed by placing the cursor on
the image and typing?.
1b. After cleaning an image, place the cursor on the center of the star to get its approximate coordinates. Enter those values, as read off the image display window, into the
imcntr task. Redirect the results to a file called “imcntr.out.” Example:
imcntr u5if3101r.c0h 444 424 >> imcntr.out
Perform steps (1a) and (1b) for all images before proceeding. Make sure they’re listed in
“imcntr.out” in the right order (as you would see it if you ran ls *.c0h).
2. The task runtvmark draws the aperture around the star for each image to make sure it
was correctly centered by imcntr, and also allows you to double-check that no cosmic
rays or hot pixels are within the aperture and sky area of the star. To run, type
runtvmark
Note: if runtvmark crashes for some reason and needs to be run again, be sure to
remove the directory “ctrs” and the file “inlist” before re-running runtvmark.
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Technical Instrument Report WFPC2 2002-007
3. Run the task checksat to make sure the stars are not saturated. This task creates two
files: “sat.cent” and “sat.centc1h” (containing minimum and maximum values in a
small area around the star, from the image and data quality files respectively). To run,
type
checksat
Inspect the “sat.cent” file to make sure that all pixels are not saturated. Saturation
occurs at 4096 DN, but since the mean bias level, about 300 DN, is subtracted during
calibration, be on the lookout for pixels with values greater than 3600 DN. If that
occurs, check the “sat.centc1h” file or the data quality file to see if that particular pixel
is saturated (saturation is flagged with a value of 8 in the data quality file).
If there are no problems with the images, go ahead and delete the data quality (.c1h)
files. If a star has a saturated point, remove that image and its data quality file from the
directory, and edit it out of the “imcntr.out” file.
4. Run the task dochop to trim the images to a 200x200 size, centered on the star. The
full-size images are stored in a directory called “bigdir” and can be deleted at a later
time. To run, type
dochop
5. The task runphot uses phot on each image to get the counts for the stars. The output
for each image is “<imagename>.c0h.mag.” To run, type
runphot
6. Run the task getcounts to create an STSDAS table containing the countrate and other
important information about the images. You will be prompted for your initials and the
table name. To run, type
getcounts
7a. Edit the table to add a column (called “decon_date”); this is the date of the last decontamination (in Modified Julian Date) before the observation was taken. This date can
be obtained from http://www.stsci.edu/instruments/wfpc2/Wfpc2_memos/
wfpc2_decon_dates.html.
7b. Then compute the number of days that have elapsed between the observation and the
last decontamination that was run before the observation. This is done by subtracting
the decontamination date (column “decon_date”) from the date of the observation (in
Modified Julian Date, column name “mjd”). The result is written to a column called
“dsd” (days since decon).
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Technical Instrument Report WFPC2 2002-007
7c. Enter the proposal ID (column name” proposid”). The proposal ID for the data can be
obtained from the image’s header file.
Example:
tcalc phot_table.tab decon_date “52464.0165”
tcalc phot_table.tab dsd “mjd-decon_date”
tcalc phot_table.tab proposid “9589”
Appendix B
The IRAF and igi scripts used to generate the photometric monitor throughput trend
plot (see figure 2) was originally written by Christine Ritchie, and later modified by the
first author. An archive of the plots and data used to generate it, stored in time-stamped
directories, can be found at /data/wfpc14/PHOT_MON/apr94_to_now_plotdir. Also, an
archived copy of the scripts is stored at /data/wfpc14/PHOT_MON/
photmon_software_archive/plot_files.
For each new plot, copy the scripts, input data, and the directory “safe” (contains special data points that followed telescope safings) from the previous run of the plot, to the
working directory. Then, append the latest data for PC and WF3 to the input tables from
the previous plot run, and rename them to reflect the date of the latest observations.
For example, in /data/wfpc14/PHOT_MON/apr94_to_now_plotdir/2002/jul02/, these
will be the input files for the procedures:
all_pc_till_02jun17.tab
all_wf3_till_02jun17.tab
The first thing to be done is to run the procedure dorattab5563. This task takes the
above-mentioned input tables and breaks it up into smaller tables for each filter and chip
configuration, giving each table specific names:
pc1tempout1.tab
pc1tempout2.tab
pc1tempout3.tab
pc1tempout4.tab
pc1tempout5.tab
pc1tempout6.tab
pc1tempout7.tab
pc1tempout8.tab
pc1tempout9.tab
wf3tempout1.tab
wf3tempout2.tab
wf3tempout3.tab
wf3tempout4.tab
wf3tempout5.tab
wf3tempout6.tab
wf3tempout7.tab
wf3tempout8.tab
wf3tempout9.tab
<--<--<--<--<--<--<--<--<---
F160BW data
F170W data
F218W data
F255W data
F336W data
F439W data
F555W data
F675W data
F814W data
It also normalized the data to a set of pre-defined datasets taken on June 14, 1994.
The task is run to produce the tables that were listed above:
cl> task dorattab5563 = dorattab5563.cl
cl> dorattab5563
Input table name: all_pc_till_02jun17.tab
Root for normalization (ex. U2A70R): U2A70R
Camera (pc1 or wf3): pc1
31
<--- define the task
<--- to run, simply type task name (without .cl)
<--- the user is prompted for input filename,
<--- rootname used to normalize data, and
<--- chip ID.
Technical Instrument Report WFPC2 2002-007
rootname ?= ’U2A70R’
<--- The following is displayed on the screen.
working on out1
table pc1tempout1
column name changed from ‘errdiv’ to ‘raterr1’
table pc1tempout1
column name changed from ‘datdiv’ to ‘ratdat1’
working on out2
table pc1tempout2
column name changed from ‘errdiv’ to ‘raterr2’
table pc1tempout2
column name changed from ‘datdiv’ to ‘ratdat2’
...
working on out8
table pc1tempout8
column name changed from ‘errdiv’ to ‘raterr8’
table pc1tempout8
column name changed from ‘datdiv’ to ‘ratdat8’
working on out9
table pc1tempout9
column name changed from ‘errdiv’ to ‘raterr9’
table pc1tempout9
column name changed from ‘datdiv’ to ‘ratdat9’
Run the task dorattab again, this time on the PC table (using the same rootname for
normalization, U2A70R.)
The script is run as follows to create a metacode file, then a postscript file:
igi < bot >G plot
igi < top >>G plot
gkimo plot nx=2 ny=1 rot+ fill+ >G plotfile
psikern plotfile device=psi_def output=plot.ps
Appendix C
All photometric monitor data is stored at /data/wfpc14/PHOT_MON/. The data is
organized by program ID. Within each program directory, sub-directories are found for
each photometric monitor visit, time-stamped with the observation date. Also, there is a
table in each program directory containing all the data for that program. For instance:
ls -F /data/wfpc14/PHOT_MON/8933
02feb23/
8933_02feb23_02may18.tab
02may14/
readme
02may18/
Each time-stamped directory contains data from a visit taken on a specific date. The
IRAF table is a summary of all photometric monitor data for that particular program.
Since this program, 8933, is completed, this table will no longer be modified. (If the program is still active, the table will contain all data from observations that have already
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Technical Instrument Report WFPC2 2002-007
executed). The file “readme” contains issues that affected this program. In the case of
8933, it is a reminder that visit 8933G3 was withdrawn.
A suite of simple scripts were written to format the photometric monitor data into an
online database. The main directory for running the scripts is at
/data/wfpc14/PHOT_MON/www_update_dir
•
The subdirectory FIXED contains photometric data for completed programs. This data
are stored in two ways.
- The tables pc.tab, wf2.tab, wf3.tab and wf4.tab contain all the data for all completed programs.
- In the sub-directories PC, WF2, WF3, and WF4, data from completed programs
are stored in tables by program ID.
•
The directory UPDATE_EACH_MON contains data from the currently-active program, and needs to be updated as new observations arrive. When that active program is
finished, it will be moved to the FIXED directory to make way for the next active photometric monitor program.
- the table of all observations from an active program is copied to
UPDATE_EACH_MON. For instance, if the currently-active program is 8934, the
table containing observations taken to date in the program directory at /data/
wfpc14/PHOT_MON/8934 is copied to UPDATE_EACH_MON.
ls /data/wfpc14/PHOT_MON/8934
02jun11
8934_02jun11_to_02jun17.tab
02jun17
So far, only two visits in this program have executed and all the results obtained so
far are in “8934_02jun11_to_02jun17.tab.”
!cp /data/wfpc14/PHOT_MON/8934/8934_02jun11_to_02jun17.tab /data/wfpc14/
PHOT_MON/www_update_dir/UPDATE_EACH_MON
-
In this directory is a script called “run_this.cl.” It takes the summary table from the
active program and divides it by chip ID. (Note: whenever a new program starts,
this script needs to be edited to put the new proposal ID and new directory where
its data is stored).
To run it, simply type
cl < run_this.cl
•
Next, go to /data/wfpc14/PHOT_MON/www_update_dir/scr
This directory contains several scripts
calc_pc.cl calc_wf3.cl create_www.cl norm.cl
runawk
calc_wf2.cl calc_wf4.cl format.cl
sort.cl
The main script that calls others is “create_www.cl.”
•
The first script called by the main routine is “sort.cl.” This task merges the old data (in
subdirectory FIXED) with the data from the current program (in subdirectory
UPDATE_EACH_MON). It then sorts all the data into subdirectories by chip ID.
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Technical Instrument Report WFPC2 2002-007
•
After sorting the data by chip and filter, the data is normalized in the scripts
“calc_pc.cl,” “calc_wf2.cl,” “calc_wf3.cl,” and “calc_wf4.cl.” Each chip/filter combination is normalized to a specific observation documented in these scripts.
•
The last script run is “format.cl” which takes the results from “calc_pc.cl,”
“calc_wf2.cl,” “calc_wf3.cl,” and “calc_wf4.cl,” and formats it to create the database
that is posted online.
•
The final step is to take a copy of the photometric monitor memo that’s posted on-line,
in html format, update the memo text, and replace the old database with the new one
created in the previous step.
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