+--------------------------------------------------------+ | STScI Analysis Newsletter (STAN) | WFPC2 | 20 April 2007 +--------------------------------------------------------+ CONTENTS: 1. New WFPC2 Phase II Observation Strategy Web Page 2. Recent Progress on the WF4 CCD Anomaly 3. WFPC2 Calibration Plans for Cycle 16 4. Updated Dark Reference Files for 2006 - 2007 +--------------------------------------------------------+ 1. New WFPC2 Phase II Observation Strategy Web Page We have created a new web page with advice about WFPC2 Phase II Proposal strategies. At the moment it primarily covers dithering, CTE, and the WF4 CCD anomaly. We may add other topics depending on the range of questions we receive from proposers in the upcoming weeks. The page is available at: http://www.stsci.edu/hst/wfpc2/wfpc2_phase2.html +--------------------------------------------------------+ 2. Recent Progress on the WF4 CCD Anomaly During Dec. 2006 - Feb. 2007 the bias levels in the WF4 CCD were again heading towards zero, and an increased possibility of blank images. On 27 March 2007, the operating temperature of the WFPC2 electronics was lowered by 1 deg C, and WF4 was again returned to near-normal operation. This is the third successful temperature reduction we have performed (others being in Jan. and Feb. 2006), and we have yet to see any serious negative side effects of the temperature reductions. This gives us some confidence that we can keep the WF4 CCD alive until Servicng Mission 4. A side effect of the temperature reductions is that the relative positions of the four CCDs in the HST focal plane move by about 0.01 arcsecond for each of these 1 deg C reductions. This may have some small effect on projects needing accurate chip-to-chip astrometry. We plan to calibrate these astrometric changes later in the year and update the CCD offset table. Details of these temperature reductions can be found in a new Instrument Science Report "Temperature Reductions to Mitigate the WF4 Anomaly" available at: http://www-int.stsci.edu/instruments/wfpc2/Wfpc2_isr/wfpc2_isr0701.pdf For most observers, the primary impact of the WF4 anomaly will be low photometric counts in the WF4 CCD during periods of low bias values. Work is underway to incorporate photometric corrections in the WFPC2 calibration pipeline later in 2007. Until then, correction equations and scripts are available and can be manually applied to the data. These corrections are accurate to about +/-2%. Please contact help@stsci.edu for more information. +--------------------------------------------------------+ 3. WFPC2 Calibration Plans for Cycle 16 The current WFPC2 plans for Cycle 15+16 and instrument closeout were created in the fall of 2006. These are available at http://www.stsci.edu/hst/wfpc2/analysis/WFPC2_cyc1516_cal_plan_final.pdf In view of the increased utilization of WFPC2, we will likely revise and expand these plans in the coming months. One likely change is an increased effort to calibrate CTE effects for extended targets. Observations of an Abell cluster and part of the HDF field are planned to study CTE effects. These new data would be compared with previous observations of the fields. We would like to hear from any observer who feels some specific calibration should be added or augmented in our planning. +----------------------------------------------------------+ 4. Updated Dark Reference Files for 2006 - 2007 We have generated new WFPC2 dark calibration reference files for the period 19 June 2006 to 26 Feb. 2007. Observers with data within this period, and wishing to utilize the new files, should re-retrieve their data from the HST archive; the new retrieval will automatically be processed with these new reference files. These will give improved removal of hot and warm pixels. After February 2007 we have been making new dark reference files within 30 days of new science observations, and plan to continue this throughout Cycle 16. +----------------------------------------------------------+ | Visit the ACS and WFPC2 websites for more news: | ACS: http://www.stsci.edu/hst/acs | WFPC2: http://www.stsci.edu/hst/wfpc2 | Need help? http://www.stsci.edu/hst/acs/help.html | or send your questions to the Help Desk: help@stsci.edu +----------------------------------------------------------+ | To subscribe or unsubscribe to this STAN, send a message | to majordomo@stsci.edu with a blank subject line and | the following in the body: [un]subscribe acs_wfpc2_news"> | Previous ACS and WFPC2 STANs are archived at: | ACS: http://www.stsci.edu/hst/acs/documents/newsletters | WFPC2: http://www.stsci.edu/hst/wfpc2/documents/newsletters +----------------------------------------------------------+ | The Space Telescope Science Institute is operated by the | Association of Universities for Research in Astronomy, | Inc., under NASA contract NAS5-26555. +----------------------------------------------------------+
