A reminder about some changes for ASCA AO-2

["Charles Day, US ASCA GOF, NASA GSFC" <DAY@heagip.gsfc.nasa.gov>]

This bulletin is to remind proposers about a few changes that have taken
place between the first and second ASCA NRA. Mentioned are:

1) RPS is now called APS2
2) The impact of hot and flickering pixels
3) New response matrices for simulations
4) Special ASCA events at January's AAS meeting

Questions about the issues raised in this bulletin, and other ASCA
issues, should be sent to ascanra@athena.gsfc.nasa.gov.


1) RPS IS NOW CALLED APS2. The Remote Proposal Submission software,
   RPS, has become APS2, which stands for "ASCA Proposal Submission,
   AO-2." This cosmetic change emphasizes the fact that a new version
   of the program has to be used for each mission and for each AO. When
   the AOs from various missions overlap, this is obviously desirable.
   
   APS2 can be obtained via anonymous FTP at:

      legacy.gsfc.nasa.gov

   In the directory:

      asca/nra_info/aps2


2) HOT AND FLICKERING CCD PIXELS. During the Performance Verification
   phase it was discovered that the SIS CCDs are afflicted by "hot and
   flickering pixels," that is, single pixels that contain false
   events. The good news is that the false events can be completely
   removed on the ground during data reduction. The bad news is that
   they are included in the telemetry, thereby wasting space that would
   otherwise be occupied by real data. For the observer and proposer,
   the presence of hot and flickering pixels significantly limits the
   count rate that can be telemetered without saturation. This, in turn,
   restricts the choice of mode and telemetry bit rate. Low bit rate,
   for example, can no longer be used, regardless of source strength,
   since all the telemetry is occupied by hot and flickering pixels.
   Obviously, careful attention must be paid to count rate and modes
   when proposing bservations, especially for moderate-to-bright
   extended sources (the more CCD chips exposed, the higher the
   telemetry).

   As for AO-1, we do not require proposers to possess detailed
   knowledge of SIS modes; however, AO-2 proposals that are simply
   infeasible cannot be accepted. In order to ensure that the available
   telemetry can accommodate your proposed observation _and_ the hot and
   flickering pixels, we recommend you determine the SIS count rate
   using PIMMS and then consult the table below which shows the maximum
   count rates that can be observed in the various combinations of modes
   and bit rates without saturation. Note count rates are for ONE SIS
   and in counts per second. Note also that this table supersedes the
   hot and flickering pixel rates built into the current version of
   PIMMS.

        MAXIMUM COUNT RATES OBSERVABLE IN SIS WITHOUT SATURATION

             --------------------------------------------
             |                                          |
             |               1-CCD     2-CCD     4-CCD  |
             |                                          |
             |  Faint,  H     51        23.5      11.3  |
             |  Faint,  M      2.5        *         *   |
             |                                          |
             |  Bright, H    231       113        56    |
             |  Bright, M     22.5       9.3       4.2  |
             |                                          |
             |  Fast,   H    477          -         -   |
             |  Fast,   M     51          -         -   |
             |                                          |
             --------------------------------------------

   Here, "*" means that the combination of mode and bit rate cannot be
   used without saturation, even if just background is observed. The
   entry "-" means that we do not have an estimate of the limit since
   Fast mode is conventionally used only with 1-CCD mode.

   As shown by the numbers in the table, the maximum count rate is
   severely restricted only in 4-CCD mode. For example, the Perseus
   cluster, which fills the SIS field of view and is detected at 40 SIS
   cps, cannot be observed in 4-CCD mode except in Bright mode with high
   bit rate. In fact, Perseus cannot be imaged in medium bit rate at
   all.
   
   The GOF will send out a bulletin shortly dealing with how proposals
   that require high bit rate only will be treated.
  
   As a reminder, PIMMS (Portable Interactive Multi-Mission Simulator)
   can be obtained via anonymous ftp at legacy.gsfc.nasa.gov in the
   directory asca/nra_info/pimms.


3) NEW RESPONSE MATRICES FOR SIMULATIONS. New GIS response matrices
   based on in-flight data are now available via anonymous ftp at
   legacy.gsfc.nasa.gov in the directory asca/nra_info/responses/gis.
   
   SIS matrices will be available shortly. In the meantime, we recommend
   proposers use the AO-1 matrix which can be found in the directory
   asca/nra_info/responses/sis.


4) SPECIAL ASCA EVENTS AT JANUARY'S AAS MEETING. At next month's AAS
   winter meeting (12-15 January 1994, Washington DC), there are three
   ASCA related events, an Invited Talk, a Special Session and a Data
   Demo:

   Invited Talk: "New Results from ASCA," Yasuo Tanaka, ISAS. Wednesday,
   12 January, 4pm.

   Special Session: High Energy Astrophysics Division I: "Highlights
   from ASCA." Friday, 14 January, 10:15-11:45 am. The session will
   present scientific highlights from the mission so far.

   Data Demo: ASCA data reduction and analysis software will be
   demonstrated, as well as PIMMS and APS2. Members of the GOF staff
   will be available to answer questions about ASCA.


Charles Day, Margo Duesterhaus, Koji Mukai
ASCA GOF, NASA GSFC