ROSAT Status Report #62:
July 13, 1993
- A redistribution of MPE status report # 19
========================================================================= = = = ROSAT NEWS No. 19 --- 1-Jul-1993 = = = =-----------------------------------------------------------------------= = ROSAT Scientific Data Center at the = = Max-Planck Institut fuer Extraterrestrische Physik (MPE) = = Giessenbachstrasse, 8046 Garching, FRG = =-----------------------------------------------------------------------= = e-mail addresses (Uli Zimmermann): = = rosat_svc@mpe-garching.mpg.de (Internet) or = = MPE::ROSAT_SVC (SPAN) = = ROSAT Service Area read-access via anonymous ftp: = = ftp rosat_svc.mpe-garching.mpg.de (130.183.72.180) user: anonymous = =-----------------------------------------------------------------------= = XUV Center: 29382::GXUVDC or GXUVDC@AIT.PHYSIK.UNI-TUEBINGEN.DE = = WFC Archive access via telnet/ftp ait.physik.uni-tuebingen.de = = user xuv (password xuv_archive) = =========================================================================
SATELLITE AND INSTRUMENT STATUS
Reduced PSPC gas flow rate
The HRI was moved into the focus on June 10 for the last time in AO-3. The PSPC gas flow rate was reduced the same day. The PSPC had time until June 15th (the beginning of AO-4) to settle down at the new equilibrium. Immediately after the switch-on on June 15th an extended radioactive source calibration was started which was followed by 1 orbit of filter-wheel-closed background measurements. This procedure was repeated the next day. For the first week after the switch-on the radioactive calibrations were repeated once per day. Background measurements are taken once per week for one orbit.
The PSPC performance at reduced flow rate still looks very good. The gain dropped slightly, from channel 103 before to 100 after the switchover. The original prospected PSPC gas lifetime was until the end of November 1993, i.e. 5.5 months from the beginning of AO-4 on June 15th. Now the flow rate has been reduced from 3.8 to 2.5 ml/min, i.e. by about 35%. This leaves us a gas safety margin of 2.4+/-1 months in AO-4 if operations continue nominally.
Attitude error
2 cases have been found where - due to the reduced accuracy of the onboard gyro system - the AMCS after a slew locked on to a wrong star pattern. In both cases only 2 stars were available in the startracker field of view and the commanded star pattern (essentially star separation and the magnitudes) were fulfilled also by a nearby star pattern, about 2 degrees off from the commanded position. Both the onboard and the ground system attitude software system assumed therefore a correct pointing and could not recognize the error.
Although the problem probably happens extremely rare, every user can check the own data by looking at the lightcurve (or the Kolmogorov test printout in the protocol) of one or more of the stronger sources in the field. In such a case the lack of source photons for some time (for all of the sources in the field at the same time !) should serve as a good indicator.
If beyond the 2 known events other such cases are detected please inform us.
MISSION PLANNING
The files ao4.timeline and ao4.summary (timeline summary) are available in the ROSAT Service Area (directory timeline).
PROCESSING
A detailed investigation showed that the following 34 observations delivered by MPE to German and UK PIs have been calculated with wrong accepted times (see ROSAT NEWS No 17 from 4-MAY-1993).
UK201367P--1 WG201297P UK201383P WG201337P UK201389P WG300230P--1 UK201391P-1 WG300254P UK300285P WG300270P UK400332P WG500198P UK600465P WG500199P UK600468P-1 WG600418P WG200716P WG600436P WG200859P WG701036P WG201086P-1 WG701114P WG201094P WG701127P WG201190P WG800367P-1 WG201193P WG800368P WG201207P WG800378P WG201213P WG600453P WG201245P WG800383P
These observations will be reprocessed by the data center in the next weeks. As pointed out in ROSAT NEWS No 17, the not-accepted events are all available in the delivered datasets in the diffevents file and thus the user may also do an own screening.
WFC ARCHIVE
The online ROSAT/WFC archive in Tuebingen, available since March 93, now supports downloading of compressed WFC images and calibration maps. The archive presently contains 938 publicly availably, pointed WFC data sets and will be updated about once per month. See the help file in the archive for directions to decompress the images on your local machine. At typical FTP data transfer speeds (3 kByte/sec) copying 1 data set (1 image plus 2 calibration maps) will take no more than 1 to 2 minutes.
The archive also contains a list of all publicly available WFC observations plus a list of all sources detected in these observations (including positions, count rates and tentative identifications).
Here is how to log into the archive (located on the AIT-VAX Cluster):
The username of the archive is XUV (password: XUV_ARCHIVE).
Internet: Type
telnet ait.physik.uni-tuebingen.de (for reading log and source files)
and
ftp ait.physik.uni-tuebingen.de (for copying data to your local machine)
SPAN: Type either
$ set host 29382
or use some of the following commands
$ type 29382::xuv_archive:[xuv]readme.txt (directions how to proceed)
$ dir 29382::xuv_archive:[xuv.(dir)] (show available files/directories)
$ sea 29382::xuv_archive:[xuv](obs/source-list) "
$ copy 29382::xuv_archive:[xuv.(dir)](mydata) * (copy data/log files)
We know that a number of sites are planning to buy or have already
bought one of the new fast Alpha machines of DEC. In our data center
presently 2 of such 64-bit computers, running Open VMS and OSF, are
installed. More are to come.
On request a version of MIDAS for Open VMS is already available from
ESO. ESO is also working on a MIDAS implementation for the OSF system.
This will be the first installation of MIDAS in a 64-bit operating
system (Open VMS is presently a 32 bit system). Due to some problems
in the MIDAS Standard Interfaces with a true 64-bit OS (integer and
long integer formats) the UNIX version requires more effort and will
still take some time.
Please contact us, if you are interested in more details.
EXSAS/MIDAS
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