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WFPC2 PSF Library Help Page

Introduction:

This WWW form provides access to the WFPC2 PSF Library. All PSFs are kept online and all are available for ftp; this html interface provides a means of sorting through and selectively choosing retrieval of only those PSFs of interest. There are four basic steps to using the library:

  1. Define a subset of PSFs using qualifiers on the top html page.
  2. Select for retrieval a subset of (or all) PSFs from the tabular PSF summary presented.
  3. Generate an ftp command file for retrieval of selected PSFs.
  4. Save command file to your local work area and execute with "ftp -n ftp.stsci.edu < commandfile".

To Improve Query Response Time

To speed response time, we recommend that as many qualifiers as possible are set and that the default output is obtained first. Generally, the Default Output will be sufficient, however, if Full Output is necessary, it should be requested after the query has been made as specific as possible: due to the size of the Library, the Full Output option can take a relatively long time to retrieve and present; even Default Output can be slow if the query is too general.

No Useful PSFs in this Library?

We periodically add new PSFs to the Library, however, if there is no appropriate PSF for your specific case, we recommend a quick scan of the HST data archive. For PSFs older than ~1 year, there may be appropriate science data that could be used as PSFs. For newer PSFs, we list the WFPC2 calibration programs below that observe either a standard star or standard field; these images have no proprietary period and can be retrieved from the archive at any time.

The main Archive page can be found at:

www.stsci.edu/archive.html

Theoretical PSFs can be generated by using the TinyTim PSF simulator:

www.stsci.edu/software/tinytim/tinytim.html

CALIBRATION PROPOSALS:

Prop No.      Title:
--------------------------------------------------------------------
4616         WFPC2 SMOV FINE ALIGNMENT AND FOCUS
4749         WFPC2 SMOV RELATIVE PHOTOMETRIC CALIBRATION
4763         WFPC2 SMOV QE & THROUGHPUT MEASUREMENT
4819         WFPC2 SMOV PSF CHARACTERIZATION
5558         WFPC2 OTA DESORPTION MONITOR
5563         WFPC2 CYCLE 4 PHOTOMETRIC CAL MONITOR 1: UV/OPT STD. 
5564         WFPC2 CYCLE 4 PHOTOMETRIC CALIBRATION 2: 4 CCD 
5565         WFPC2 Cycle 4: PHOTOMETRIC MONITORING: FIELDS
5572         WFPC2 CYCLE 4: PHOTOMETRIC FILTER CALIBRATION
5629         WFPC2 CYCLE 4: PHOTOMETRIC MON.: 4-CHIP IN F170W
5646         WFPC2 CYCLE 4: CTE DITHER TEST
5651         WFPC2 CYCLE 4: F606W PSF WINGS CALIBRATION
5659         WFPC2 CYCLE 4: CTE DITHER TEST, PART II
5663         WFPC2 CYCLE 4: PHOTOMETRIC CAL MONITOR: FIELDS 
             PART II (continuation of 5565) 
6143         WFPC2 CYCLE 4 PHOTOMETRIC CAL MONITOR 1: UV/OPT STD - 
             PART II (continuation of 5563)
6179         WFPC2 CYCLE 5: PHOTOMETRIC ZEROPOINT
6182         WFPC2 CYCLE 5: PHOTOMETRIC TRANSFORMATION 
6184         WFPC2 CYCLE 5 PHOTOMETRIC CAL MONITOR UV/OPT STD 
6192         WFPC2 CYCLE 5: CTE CALIBRATION
6193         WFPC2 CYCLE 5: PSF CHARACTERIZATION
6195         WFPC2 CYCLE 5: FLATFIELD CHECK

Some more details on the calibration proposals, field targets followed
by white dwarf standard observations:

Prop ID     Target     Data Sets          Filter(s)            Exp. time
                                                               (in sec.)
----------------------------------------------------------------------------

4616        Omega-Cen     35       F555W, F814W                    30
            HD8538        48       F502N, F953N, F170W            1-4

4749        Omega-Cen     14       F300W, F547M, F569W, F606W     7-600
                                   F675W, F702W, F785LP
            A+81D266      36       F336W, F439W, F555W, F675W    0.7-26
                                   F814W, F130LP, F165LP,
                                   F185W, F255W    

4763        Omega-Cen     35       F336W, F439W, F555W, F814W     6-400
            BD+75D325    126       F122M, F160BW, F170W,          0-6
                                   F218W, F300W, F502N, F673N

4819        M67            8       F555W, F814W                    40 
            Omega-Cen    106       F555W, F814W                    40 

5558        Omega-Cen     13       F555W                           30

5565        Omega-Cen     70       F336W, F439W, F555W,          3-400
                                   F675W, F814W

5646        Omega-Cen      9       F555W                           40

5651        M67            8       F606W, F439W, F675W           2.6-230

5659        Omega-Cen     18       F814W, F439W                    40

6192        Omega-Cen     68       F555W                        40 & 1
                                   F814W                           40

6193(*1)    Omega-Cen     80       F439W, F675W, F814W            40

6195(*2)    Omega-Cen     44       F336W, F439W, F555W, F606W,    100-200
                                   F675W, F814W

5563        Feige110      18       F439W, F675W, F814W, F170W,    0-80
            GRW+70D5824  468       F555W, F160BW, F218W, F255W,
                                   F336W

5564        GRW+70D5824   10       F336W, F439W, F555W, F675W,    1-12
                                   F814W             

5572        NGC5139       18       all (except UV) filters        7-600
            GRW+70D5824  224                                      1-500

5629        GRW+70D5824  134       F170W                         40-60

5663        NGC6752/5139 267       F336W, F439W, F555W, F675W,   12-300
                                   F814W       

6143        GRW+70D5824  180       F439W, F675W, F814W, F170W,    2-300
                                   F555W, F160BW, F218W, F255W,
                                   F336W

6179        GRW+70D5824   28       all WFPC2 filters              4-300
            G191-B2B      16
            HZ-44         15
            S121-E        16
            P177-D        15
            SA95-330      14

6182        NGC5139       54       all broad and medium bandpass 10-400
                                   filters

6184        GRW+70D5824  266       F439W, f675W, F814W, F170W,    2-260
                                   F555W, F160BW, F218W, F255W,
                                   F300W, F336W, F185W

6186        GRW+70D5824  110       F160BW, F130LP, F185LP,        8-260
                                   F165LP

Notes:
------

*1 Partial execution; some visits (e.g., F336W, F555W, lost due to safing).

*2 NOTE: first image in each orbit preflashed.

FTP all PSFs in the Library at once?

Due to the size of the library, it is quickest to manually ftp all the PSFs rather than use the WWW page to select them all. Note that they are kept in both fits (*.fits) and geis format (*.r7h, *.r7d).

ftp ftp.stsci.edu
login anonymous		(use email address as password)
cd /cdbs/cdbs8/upsf
binary
prompt
mget *.fits		
  or
mget *.r7*

Image Data:

These keywords reflect the general characteristics of the WFPC2 images from which the PSF has been extracted.

  • Detector:
  • Detector refers to the camera used to image the PSF. All Cameras have 800x800 pixels. The PC, with f ratio of 28.3, has a 35"x35" field of view (or about 46 milliarcseconds per pixel) while each WF camera, with f ratio of 12.9, has 2.5'x2.5' field of view (~100 mas per pixel). For a diagram illustrating the WFPC2 Field of View as projected on the sky, please refer to the WFPC2 Handbook, Section 1.1.1.

  • AtoD Gain:
  • Gain used to take PSF image, referred to as either 7 or 15. Note that the actual gain values are not exactly 7 (or 15) and depend on the camera, ranging from 6.9 to 7.1 and 13.95 to 14.5. See the WFPC2 Handbook, Section 4.13, for detailed information.

  • Serials:
  • Keyword indicating whether clocks were ON or OFF during the PSF exposure. Most exposures are taken with clocks = OFF; clocks = ON is occasionally used when very bright targets are observed and likely to result in excess of ~10E08 electrons. Note that for clocks = ON exposures, the actual exposure time is shortened by a small amount (0.125 or 0.240 sec, not reflected in header), which can be significant for short (~30 sec or less) exposures. See also WFPC2 Handbook, Section 2.6 and Handbook, Section 7.2.

  • Filtnam1, Filtnam2:
  • Filter that was in place during the PSF exposure. Detailed information concerning the WFPC2 filters can be found in the WFPC2 Handbook, Section 3.

  • Sort Output By:
  • Output type refers to how many keywords are included in the tabular summary of selected PSFs. Default Output provides ~20 of the most important keywords (like detector, filter1, gain, clocks, origin, x and y center, observation date, exposure time, PSF dataset name, saturation status, PSF peak intensity, dimensions of PSF image and proposal ID number).

    Full Output will retrieve the more than 110 keywords associated with each PSF, which can take correspondingly longer to retrieve and present than Default. The Full Output keywords are all the standard WFPC2 science header keywords (image description, instrument status, calibration files, exposure and target information and group parameters) as well as new PSF-specific keywords (e.g., x and y center, peak intensity, RA and Dec of PSF, etc).

    If Full Output is required, we recommend refining the query using Default Output and choosing Full only as the last query; this will dramatically improve response time.

    Sample PSF Header.

    Exposure Info:

  • Rootname:
  • Rootname refers to the original WFPC2 image from which the PSF was extracted. WFPC2 image rootnames are always 9 letters long. The first indicates instrument used ('U' for WFPC2), the next 7 letters are unique for each proposal, and the last letter provides an indicator of the transmission type. The most common forms of transmission are: r=realtime, t=tape recorded, m=merged, p=retransmitted tape recorded.

  • From, To:
  • Date the image was taken; note that the format must be dd-mmm-yyyy (no preceding spaces).

    Setting only a "from" date will result in a search for PSFs taken on that single day only.

  • Exptime:
  • Exposure time in seconds. This keyword may be qualified with '>' or '<', to restrict selection of PSFs.

  • FGS lock:
  • Commanded FGS lock of original WFPC2 image, either fine-lock, coarse track, gyros, or unknown. Fine lock (2 FGSs in fine lock) is used by default now, since coarse track is now known to be detrimental to the FGSs. Fine lock generally keeps jitter down to ~0.007" RMS; absolute pointing accuracy will be on the order of 1". In gyro mode, the pointing can drift from 1-5 mas/sec and the absolute accuracy on the order of 2-100".

    For more information on guiding modes, see the annaul Call for Proposals.

  • Expflag:
  • Expflag indicates whether the exposure was interrupted for some reason. To restrict search to uninterrupted PSFs only, select Normal.

    Target Info:

  • Right Ascension:
  • Right ascension of PSF star. Value was obtained by running STSDAS metric on original WFPC2 imaging, providing x and y pixel center for PSF. Note that a region of sky may be specified by inputting a central RA and Dec, along with a search radius.

  • Declination:
  • Declination of PSF star. Value was obtained by running STSDAS metric on original WFPC2 imaging, providing x and y pixel center for PSF. Note that a region of sky may be specified by inputting a central RA and Dec, along with a search radius.

  • Search Radius:
  • Search radius to use in combination with RA and Dec; note that the current implementation is to search a box with sides 2 x search radius in length, centered on the requested RA and Dec.

  • Targname:
  • Target name from TARGNAME keyword in original WFPC2 image. For fields, this keyword will reflect name of field and not individual stars in the fields (e.g., calibration field Omega Cen: all PSFs from this field will have a target name of Omega Cen).

  • Proposal ID:
  • Proposal number for which the original WFPC2 image was taken. More details on any given proposal are available via the public proposal information page. Calibration proposals are also summarized in the WFPC2 Instrument Handbook.

  • Spectral Type:
  • Spectral type of PSF, if known. Unless the target was a single star and the proposer provided spectral information in the proposal, this field may not be populated.

    PSF Characteristics:

  • PSF Origin:
  • Pedigree of PSF, either an observed WFPC2 PSF, a PSF computed using TinyTim, or a composite PSF generated from a set of observed PSFs. As of Nov. 1996, only single observed PSFs are in the library.

    TinyTim software is available at: www.stsci.edu/software/tinytim/tinytim.html

  • Peak intensity:
  • Intensity of peak pixel in PSF (DN).

  • Peakfit:
  • Peak intensity of PSF (DN), derived by fitting a Gaussian to an area of radius 5 pixels around the center of the PSF.

  • X center:
  • X position of the center of the PSF on the CCD (in pixels). Origin for each chip is the corner closest to the pyramid apex; X axis runs perpendicular to the readout direction, Y increases opposite the readout direction. Also see Figure 1.1 in the WFPC2 Handbook, Section 1.1.1. NOTE: in that figure, readout direction is marked with small arrows near pyramid apex. X and Y label in Figure 1.1 do NOT refer to X and Y positions on chip but refer to POSTARG directions.

  • Y center:
  • Y position of the center of the PSF on the CCD (in pixels). Origin for each chip is the corner closest to the pyramid apex; X runs perpendicular to the readout direction, Y increases opposite the readout direction. Also see Figure 1.1 in the WFPC2 Handbook, Section 1.1.1. NOTE: in that figure, readout direction is marked with small arrows near pyramid apex. X and Y label in Figure 1.1 do NOT refer to X and Y positions on chip but refer to POSTARG directions.

  • Radius:
  • Radius to be used in conjunction with x and y center; note that current implementation retrieves PSFs in box centered on x and y center, with sides of length 2 x PSF Radius specified.

  • Relfocus:
  • This keyword provides an estimate of relative focus at the time of the original WFPC2 image.

    The RELFOCUS values in the PSF header is determined from an average fit of the focus monitoring data based on the "phase-retrieval" method, with no correction for orbit-to-orbit variations in the focus (known as "breathing"). No breathing correction could be preformed for data taken before July, 1995, since temperature data was not easily available at that time. Only PSFs taken after July, 1995 will have the breathing correction applied to the relative focus value. See Instrument Science Report OTA-18 for details on the focus history of HST and the "breathing" correction (Casertano, 1995). The r.m.s scatter around the average fit is roughly +/- 2 microns, while the scatter for points with the breathing correction is close to +/- 1.3 microns.

    PLEASE NOTE: Due to data drop outs and other intermittent glitches, temperature data is not always available after July, 1995. Thus, some PSFs may still have no secondary mirror temperature information and their RELFOCUS value will be that of the orbital average (i.e. phase retrieval value) without the breathing correction.

    To date, focus excursions of greater than 5 microns have been very rare, thus a search from say, -8 to 8 microns will find all PSFs in the database with RELFOCUS values. There is no need to enter "<" or ">" signs in the input boxes, and if only one textbox is filled, a search of all PSFs within 1 micron of that value will be performed.

    See also the Observatory Support Group's focus page.

    NOTE: If an observations RELFOCUS is unknown, a value of 9999.99 is added to the header.

  • Saturated:
  • This keyword is set to YES if any pixels in the PSF exceeded 4095 in the raw data file. Although full well capacity is 90,000 electrons per pixel, the 12 bit A-to-D converters limit WFPC2 to DN values of 4095, so saturation occurs at 27,000 electrons (gain 7) and 53,000 electrons (gain 14).

    Any PSF with saturated pixels (bitflag=8, in the original calibration image's data quality (.c1h) file), had those pixel values replaced with a value of -100. This will allow users to quickly identify saturated pixels within the PSF.

  • PSF Sampling:
  • Subsampling used to produce PSF.

  • V2 RMS, V2 P2P, V3 RMS, V3 P2P:
  • The RMS values are the standard deviations of the dominant guide star's jitter along V2 and V3, in units of milli-arcseconds. The peak-to-peak values refer to the maximum amplitude of the jitter in V2 and V3 (in mas). These 4 parameters come from the Observation Logs; they will not be populated prior to ~ Oct 1995 (before that time, the logs were not generated). For more details on interpreting these keywords, please see the Observation Logs Manual, available at: www.stsci.edu/hst/observatory (For V2/V3 specific keywords).