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Hubble Space Telescope

S T A N / W F P C 2 - Number 2, December 1994



A new WFPC2 history file has been added to STEIS (Space Telescope Electronic Information System).

This file provides a chronological history of the WFPC2, including:

  1. Decontaminations
  2. Darks and Superdarks
  3. Focus Changes
  4. Temperature Changes
  5. Changes to the Pipeline
  6. Safings
  7. Miscellaneous Items

It is designed to provide observers with information about the state of the WFPC2 when their observations were taken. The most important change occurred on >>> APRIL 23, 1994 <<<, when the operating temperature was changed from -76 C to -88 C in order to minimize the CTE (Charge Transfer Efficiency) problem and the growth of hot pixels. Care should be taken not to use inappropriate calibration files that cross this date. Each item includes a short description of how it might affect the observer.


We draw your attention to these papers, based on WFPC2 data, that will appear in the next few months. This list includes all preprints received by the STScI Library not yet published in the journals. Please remember to include our Library in your preprint distribution list.

"An Image Restoration Technique for the Removal of Cosmic 
Ray Hits from Dithered Images"
Freudling, W.; 1995 PASP, in press.

"Very Low Mass Stars and White Dwarfs in NGC 6397"  
Paresce, F.; De Marchi, G.; Romaniello, M., 1995 
ApJ in press.

"Structure and Photometry of an I < 20.5 Galaxy Sample from 
the HST Medium Deep Survey"
Phillips, A.C.; Bershady, M.A.; Forbes, D.A.; Koo, D.C.; 
Illingworth, G.D.; Reitzel, D.B.; Griffiths, R.E.; Windhorst, 
R.A.; 1995, ApJ in press.

"Stellar r Photometry in the Inner Bulge of M31 Using the 
Hubble Space Telescope Wide Field Camera"  
Rich, R.M.; Mighell, K.; 1995, ApJ in press.

"Discovery of Cepheids in NGC 5253: Absolute Peak Brightness 
of SNe Ia 1895B and 1972E and the Value of H_0"  
Saha, A.; Sandage, A.; Labhardt, L.; Schwengeler, H.; Tammann, 
G.A.; Panagia, N.; Macchetto, F.D.; 1995, ApJ in press.


The Observation Log files contain a specialized set of pointing and engineering data associated with each science exposure (including the jitter information).

Observation Log files for most science observations since October 20 1994 have been produced by the pipeline and written to the HST archive. Starting at the end of February 1995, these files will also be included on the data tapes sent to observers.

A more detailed description of the Observation Log can be found in an article by O. Lupie, B. Toth and S. Baum in the forthcoming December issue of the STScI Newsletter.

The Observation Log header file contains, among other things:

The header also alerts the observer to slews occurring during an observation and reports anomalies that can compromise the integrity of the science data (e.g., degraded guide star acquisitions, losses of lock), or result in a failed observation (e.g., instrument or vehicle safings, failed target acquisitions).

The data portion of the log file contains pointing data and other parameters that are traced as a function of time during an exposure including the `jitter', i.e., the movement of the aperture as a function of time during the observation.

Additional information about the Observation Log Files and how to retrieve them from the HST Archive can be found within the HST Archive Page under the STScI home page ( Once in the archive pages, click on Retrieving HST Data and refer to the section on Observation Log Files.


Any questions about the scheduling of your observations should be addressed to your PRESTO contact. If you do not know who this person is, PRESTO's Mosaic page ( contains that information.

Post-Observation questions should be addressed to the WFPC2 Analysis Team, if your program is covered by this pilot project, or

Comments, questions, requests for issues, additions or deletions to the mailing list, etc. can be e-mailed to

The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.