ASCA data are being archived at the National Space Science Data Center on the NASA Data Archive and Distribution System (NDADS) near-line system. Data first became publicly available on November 15, 1994, and consist of data from the initial 8-month Performance Verification (PV) period of the mission. Data from the Guest Observer part of the program, which began after the completion of the PV period of the mission, should begin to become publicly available in May 1995. Data will initially be released in 1-month batches, around the 15th of each month. As the archive population becomes routine, the releases will be made more frequent, on a weekly basis.
ASCA data on NDADS are organized by the 8-digit observation sequence number. The data files for a single observation sequence have been grouped into six data-types (AUX, RAW, TELEM, SCREENED, UNSCREENED, and PRODUCT) and archived on NDADS in UNIX TAR containers. Most of the component files within each TAR container have been compressed (*.Z extension) using the UNIX compress utility. The size of each TAR container varies substantially depending on the particular sequence number and data type, but may be as large as 50-200 mB and have several hundred component files. The individual ASCA data files are archived in FITS format.
Also archived on NDADS are six logs (listings) of the files within each TAR container. These logs are derived from the original "Bills of Lading" (BOLs) delivered from the project and contain the following fields; original file name delivered by the project, compressed byte count, decompressed byte count, original release date as supplied by the ASCA project, an archive flag used to ingest the data, and the astrophysical object name. These logs are archived as ASCII files separate from the TAR container files (NDADS data-type of 'LOG'). Further details on the ASCA data are available from the ASCA WWW pages referenced below.
To: NDADSA::ARCHIVES (or email@example.com) Subject: HOLDINGS ASCAThe NDADS holdings file also contains more detailed information on the ASCA data formats, such as how to request ASCA data from NDADS and how to extract the individual data files once the user has copied the files to their home computer or another location.
NDADS requests for ASCA data should include the NDADS entry-id's (8-digit observation sequence number's), the data-type (AUX, SCREENED UNSCREENED, PRODUCT, LOG, TELEM, and RAW) and the project name (ASCA). For example:
To: NDADSA::ARCHIVES (or firstname.lastname@example.org) Subject: REQUEST Project_Name Data_TypeIn the body of the mail message list the sequence number(s) you wish to request. A request for a particular object may also be submitted instead of the 8-digit observation sequence number. If a particular object was observed multiple times then more than one observation sequence will be returned. Requests for more than one data-type must be submitted separately.
http://nssdca.gsfc.nasa.gov/asca/asca.htmland then connect to "ASCA Data Archives at the ADF/NSSDC." This allows you to connect to a form for requesting ASCA data. You may then electronically transfer the data via default DECnet or ftp to the node of your choice. This process is similar to the NDADS/ARMS E-mail procedure.
http://heasarc.gsfc.nasa.gov/0/docs/asca/ascagof.htmland then connect to "How to access the ASCA archive."
Questions concerning how to access ASCA data on NDADS may be sent to Nancy Oliversen at email@example.com.