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UK ROSAT/LEDAS Electronic Newsletter No. 13July 26 1999Issued by the ROSAT Guest Observer Centre & the Leicester Database and Archive Service (LEDAS) University of Leicester ledas-www.star.le.ac.uk ContentsLEDAS News
ROSAT News
LEDAS NEWSLEDAS Phase IIIThe LEDAS project, having successfully provided a high energy astrophysics archive data since 1992, was awarded a further three years funding from January 1999. This allows us to continue to support the UK community by the provision of a national X-ray satellite data holding, increasing in scope with the addition of highly valuable ASCA and Chandra data, and with improved data server hardware and software. In this era of ever-increasing dataset volumes and transatlantic internet charges the argument for local provision remains strong. LEDAS data continues to be much in demand, recently we have been serving 1100 data files per month; this can only increase as the exciting data from the recently launched Chandra becomes available. New LEDAS hardware and website In order to maintain the high quality of service provided by the LEDAS, we have augmented our existing hardware by the purchase of a new Alpha server. The new machine will provide the necessary processing power and disk serving capability to allow the LEDAS to improve upon its existing services, and to develop new ones, over the next three years. This machine is now operational and users should find an immediate increase in the speed and reliability of all LEDAS services, in particular with DSS and ARNIE requests. The installation of the new server has been timed to coincide with a repackaging of the LEDAS web site. The layout of the LEDAS pages has been altered to incorporate navigation bars and section headings. These changes provide easier orientation within the LEDAS site without a significant impact on download time. The URL for the LEDAS website remains: http://ledas-www.star.le.ac.uk/
The Chandra science mirror at LEDAS The LEDAS has been providing a mirror of the Chandra Science web pages, originating from the Chandra X-ray Observatory Center (CXC) at CfA, since April 1999. This mirror provides the UK astronomical community with faster and more reliable access to the most critical on-line information on the Chandra mission than can be obtained by direct access to the CXC site. The LEDAS Chandra Science mirror is a precursor to the next major project for the LEDAS: the creation of the LEDAS Chandra Data Archive. This archive will be a mirror of the high-level data products from the Chandra public data archive at CXC, the proposal generation software and the analysis software. We plan to replicate all public data at Leicester using an automated system, providing real-time archive updates. Chandra dataset volumes are such that it will barely be possible for those in the UK to obtain them directly from the CXC site in the USA. This archive is expected to be operational by the time usable scientific data begins to flow into the public domain (autumn 1999). The URL of the Chandra mirror is: http://ledas-cxc.star.le.ac.uk/ The ASCA public data archive was originally released by LEDAS in November 1998, the product of a collaboration with HEASARC (USA) and ISAS (Japan). This service provides the UK with fast access to hard X-ray imaging data with good spectral resolution. The archive contains data in both raw and processed formats, with quick-look gif images in hard and soft spectral bands. The LEDAS ASCA public data archive was updated in May 1999 with datasets that had become public in the six months following the initial release. Regular updates will continue to occur at approximately six-monthly intervals. The end of the ASCA mission is expected in spring 2000, and so updates will continue to spring 2001. The ASCA archive will eventually contain all public data, a total of some 3000 datasets. The UK ASCA public data archive can be found at: http://ledas-www.star.le.ac.uk/asca/ The LEDAS is hosting a mirror of the distribution files for PIMMS, the popular X-ray mission simulator. We are also hosting W3PIMMS, the on-line version. This was updated to Version 2.7 in July 1999. These services can be found at: http://ledas-www.star.le.ac.uk/pimms/
ROSAT NewsThe ROSAT post-mission phaseThe ROSAT observatory was finally switched off on 12 February 1999 following severe damage to the HRI caused by an accidental near-Sun pointing on 20 September 1998 (see MPE ROSAT NEWS Nos. 66 & 67 and press release, at http://ledas-www.star.le.ac.uk/rosat-goc/). In the intervening period, a number of scientific observations were conducted with the PSPC and the WFC, and final engineering tests and calibration observations were conducted. The ROSAT Project in the UK (at Leicester and Birmingham Universities and at RAL) will continue to be funded by PPARC until the end of March 2000. Work is in progress to complete the post-mission activities by that time. These tasks include checking the completeness and long-term accessibility of the various databases, and updating the data-analysis software, calibrations and documentation (including Web pages). In addition, the UK Guest Observer support from Leicester University continues, and services typically several queries per month. The legacy of ROSAT, almost eight years of X-ray/EUV observations covering of order 9000 target fields on the sky, is publicly available worldwide, and maintained by the ROSAT archive centres in the three participating countries -- LEDAS (UK), MPE [and Tuebingen for EUV data] (Germany) and GSFC/HEASARC (USA). Aspect error in SASS processing of HRI images There is a bug in the in the standard processing of HRI images (SASS) which affects all ROSAT HRI observations prior to 17 Jan 1997. It has been found that the adopted aspect solution may be offsetting photon positions by a mean of 3.5 pixels from their correct locations. An off-line fix is available and newly processed data will be unaffected. For a detailed description of this bug, the cause, and the fix, please see: http://ledas-www.star.le.ac.uk/rosat-goc/rosstatus178
Keith Sohl - LEDAS support scientist - kbs@star.le.ac.uk
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