ROSAT Guest Observer Facility

ROSAT Status Report #28

July 9th 1992


Contents

  • Goddard Anonymous FTP
  • PSPC Spectral Analysis
  • HV
  • The Hints & Pointers Service
  • Timing Problem
  • ROSAT Workshop
  • Co-I Access to ROSAT Data
  • The ROSAT Data Archive

    Goddard Anonymous FTP

    To reach the account

    ftp rosserv.gsfc.nasa.gov
    at the ftp login prompt the username is anonymous and the password is your user identity (say your username at your home institution). The account is captive so you will see a limited range of directories.

    * Two new documents are now residing in the anonymous ftp account:

    1) The most up to date list available of the blacklist observations, ie those observations suffering a loss of exposure time due to satellite problems. This file may be found under

    /pub/AO-Info/blacklist.10June

    2) A summary document of all available ROSAT memos. These memos are mainly informal, sometimes in note form and many are pre-launch documents which contain out-of-date information. Not all of this information has been circulated by MPE as preprints. This list is intended only to give US observers an indication of what information is available at Goddard, and is in response to user requests. The list includes dates of release, giving the user an indication of how recent the information contained within the document is. While these memos are freely available on request, they were not intended as final and referenced calibration information and should not be used as such.

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    PSPC Spectral Analysis

    While the ROSAT PSPC has been extensively calibrated, on the ground and in-flight, there is still the possibility that small systematic effects can show up in high signal-to-noise data. Users should be aware that unexpected low energy absorption features have been detected in a number of sources (covering a variety of source types). The feature can be modeled as an edge of energy typically in the range ~0.2 and 0.4 keV and statistically highly significant. It is not yet clear whether these represent an instrumental effect, and a joint effort is being made by the ROSAT US/UK and MPE teams to understand these observations. Observers should be cautious about the interpretation of spectral features in the ROSAT data (particularly those of low equivalent width), unless they have a strong scientific basis on which to believe them.

    The possible origin of the effect is being investigated, including examination of the spectral response matrix. A note detailing this effect will shortly be installed in the anonymous ftp account

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    HV

    Note: The HV monitor strip plot shows considerable jitter. This is the product of the HV monitor, and not an indication of true variation in HV across the observation. The monitor is only good as a crude indicator of HV. SASS uses an interpolated value of HV, calculated from on-board calibration source measurements, to calculate the gain and hence make the PHA to PI correction for a given observation.

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    The HINTS AND POINTERS Service

    As the provider of the PROS software package ("xray" in IRAF), the Rosat Science Data Center (RSDC) at SAO is offering a direct email service for useful information on PROS functions. When we find answers to often asked questions, or when we have implemented new software solutions to longstanding problems, we plan to send this information directly to our users. These messages will also be available via anonymous ftp*, but to receive the email version, you should register with us. If your username is the one associated with your site registration, you are already registered for "HINTS & POINTERS", but we encourage other users (even at the same sites) to register.

    Mailings will not be on a regular schedule, but we envisage that they would average about 2 per month. If you would like to subscribe to our service, simply send your email address to:

    **************************************************************************
    Internet - rsdc@cfa.harvard.edu		RSDC    MS-3
    DECnet   - CFA::RSDC (6699::RSDC)	Center for Astrophysics
    UUCP	 - ...!harvard!cfa!rsdc		60 Garden St. Cambridge MA 02138 USA
    BITNET   - rsdc@cfa			tel: (617) 495-7134  FAX: 495-7356
    **************************************************************************
    
    * to access the sao anonymous ftp service:
        o   ftp -i sao-ftp.harvard.edu              # node address: 128.103.42.3
            [Name: anonymous]
            [Password: ]
    
       ftp> cd pub/pros/Hints
    

    NB: you can also obtain your own copy of the PROS USERS GUIDE by anonftp from subdir /pub/pros/PUG.

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    Timing Problem

    HRI data acquired after the 1992 Feb 26 spacecraft-clock reset event have been found to be subject to timing errors similar to those experienced by the PSPC. Prior to the Feb '92 reset, the HRI data had been free (cf. ROSAT Status report #23) of the timing error (+/- 1 sec) that affected PSPC events.

    A fix for this bug has been tested and will be installed soon, but with data acquired after Feb '92, analyses for which timescales of a few seconds or less are important may be affected and should be deferred until (or repeated after) reprocessed data become available.

    For both instruments, these problems with the SASS telemetry-decoding process stem from unanticipated time-synchronization problems introduced by the spacecraft-clock resets. Unaffected by two previous resets, the HRI software recently fell victim to this problem because the Feb '92 reset fortuitously requires an offset value that is unresolvable (within the spacecraft telemetry system 40-millisecond "sync tolerance") from 1.0 second.

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    ROSAT Data Analysis and Science Workshop

    November 4-5, 1992

    Park Plaza Hotel, Boston, Massachusetts

    The US ROSAT Science Data Center is planning a brief (1.5 days) ROSAT data analysis and science workshop. The purpose of the workshop is twofold: to allow open exchange of ideas and techniques to be used for extracting the maximum amount of information from ROSAT data, and to provide a forum for discussion of what are the most important scientific issues which ROSAT can help resolve. The scientific discussions are intended to provide insight as to how to best utilize the remaining PSPC time in AO4, which will be released around that time.

    The workshop will consist of a few invited presentations, and as many brief (10-15 minutes) contributed presentations as can be accommodated. There will also be ample room for poster presentations. Because of the limited time available, we will ask those giving oral presentations to focus on the methology used in attaining their results. Science presentations are encouraged in the form of posters. The ROSAT science support staff will participate, and we will have members of the MPE team available for a question and answer session. By tying this workshop to the end of the Astronomical Data Analysis and Software Systems (ADASS) meeting, we also will have workstations set up for demonstrations and hands-on tutorials of all ROSAT software, including IRAF/PROS, MIPS/RPS, IDL, and MIDAS/EXSAS.

    We invite all members of the ROSAT community to attend the meeting whether or not they are interested in giving talks. If you are interested in participating, please send and E-mail note to Karen Smale at ksmale@heasarc.gsfc.nasa.gov.

    Future bulletins and mailings will feature a tentative list of invited speakers and registration information.

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    Co-I Access to ROSAT Data

    The ROSAT Science Data Center recognizes the PI on an observation as the individual responsible for that observation. As such, she/he is the only person entitled to receive proprietary data. If he/she desires access by a co-investigator to a data set, the following procedure should be followed: If the data are in the US program, send a message to the US ROSAT project scientist, Rob Petre, requesting the release of those data to the co-investigator. If the co-investigator is in Germany or the UK and wants data in the ROD (German) format, the request will be forwarded to the German data center at MPE. If the data are in the German or UK program, and a US coinivestigator would like to receive the date in PROS compatible format, then the appropriate project scientist must first approve release of the data. Note that no German or UK PSPC data have been processed by the US data center (in order to catch up with the processing backlog more quickly), so there may be some delay in providing those data.

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    The ROSAT Data Archive

    ROSAT data begin entering the public domain in late summer or early fall. The initial archive will be located exclusively on the NDADS computer, run by the NSSDC at Goddard. It will be possible to request data sets through the HEASARC on-line service, through MIPS, or directly from NSSDC. Data will be made available via tape or electronically. An anonymous ftp service through the Goddard GOF and HEASARC will provide access to the images for browsing.

    In the initial archival release, all data will be in the form initially released to the PI. That means that the non-US data will be in the German ROD FITS format. The US data center will implement very shortly the capability of converting the ROD into a form usable by PROS. This capability already exists in the IDL software available through the anonymous ftp account. In addition, not all the information sent to PI's will be distributed. Source lists and the analysis of individual sources is considered too unreliable to be part of a general archive release at the moment.

    Beginning in November, the data centers will initiate a revision 1 reprocessing of all ROSAT data. The most important improvement in the rev. 1 data will be the handling of individual sources, from detection through analysis. The correction necessary for proper event timing will also be incorporated. In addition, it is likely that the Wide Field Camera aspect solution will be folded into the processing, providing aspect for some intervals for which the XRT aspect camera was unable to give a solution. For most observations, the improvement in data quality will be small, and so the initially released photon files in the archive will be adequate for most analysis. Nevertheless, in order to give a PI a fair opportunity to exploit a revised data set, revision 1 data will have a six month proprietary period attached to it.

    Rev. 1 data will be distributed in the new, "rationalized" FITS format. This is a more efficient format being developed jointly by the USRSDC and the HEASARC, to ultimately make the ROSAT data more amenable to analysis in a multimission context. Also, by the time rev.1 data are available for the archive, it is our expectation that all archival data will be available for browsing and distribution via the HEASARC on-line service.

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    Curator: Michael Arida (ADNET); arida@milkyway.gsfc.nasa.gov
    HEASARC Guest Observer Facility


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    This file was last modified on Tuesday, 14-Sep-1999 11:47:03 EDT

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