Complete Set of Unprocessed HXIS Data Stored in VMS Backup Format

Description

This data set consists of the entire production of data by the HXIS instrument, from its activation after launch through its deactivation after the SMM spacecraft lost fine pointing control (rendering HXIS data unusable). This data set was used as the primary archive, rather than a collection of processed data (so-called HIMSEL format data) because the unprocessed data are much more compact, and software to process these data is readily available. The contents of all the HXIS IPD tapes are available on 8 mm tape cartridges in DEC VMS BACKUP saveset format. Data between February 14 and November 24, 1980 (Days 45--329) are covered. One day is missing: November 6 (Day 311). The IPD tape was missing and IPD could not regenerate it. However, processed files containing selected flares on that date are included in data set 80-014A-05B. The data are counting rates in individual mini-proportional counters of the instrument (and in some cases sums of counting rates in certain combinations of counters), which may be assembled into images of solar X-ray sources in six energy bands (3.5--5.5, 5.5--8.0, 8.0--11.5, 11.5--16.0, 16.0--22.5, and 22.5--30 keV). The fields of view of the mini-proportional counters were arranged to make up a fine FOV comprised of 8 arc-sec pixels and a coarse FOV comprised of 64 arc-sec pixels. (Some other ``slit''-shaped combinations of pixel rates were also recorded.) The time resolution varied in a manner intended to match the tendency of flares to start with rapid variations and become gradual later on; when a counting-rate increase indicated that a flare was starting within the instrument's FOV, time resolution switched to 1.5 s for a few minutes, then to 4 s, and later to 9 s. Limitations of the data: in addition to daily and occasional interruptions of data collection due to changing spacecraft operational conditions (spacecraft night, deactivation during passage through the South Atlantic Anomaly (SAA), etc.), data were also limited to observations of the one or two solar active regions that were within the instrument's chosen target FOV, and consequently many flares occurred on the Sun which were not observed with HXIS, being outside the FOV. Detailed knowledge of the instrument's pointing state is important to proper use of the data, and vital when comparing HXIS images with images from other sources. Data are also sometimes contaminated with interference by high-energy particles passing through the instrument, leaving spurious image artifacts; usually isolated pixels are given a conspicuously high counting rate in an isolated time integration, but sometimes entire images are obliterated. Users should also be alert for spacecraft pointing changes during observing sequences, which sometimes introduced unreal apparent source motions. Users interested in detailed structure of the data files may consult pp. 5-35 through 5-37 of NASA Document X-565-78-20 (``Data Processing Plan for Solar Maximum Mission-A (SMM-A)''), which describes in full the original data tape format of the unprocessed data; photocopies of these pages are available, or the entire document is available on microfiche. Software to produce image maps and displays and to calibrate the counting rate values to yield photon fluxes is available from the Solar Data Analysis Center (SDAC), Mail Code 682, NASA/Goddard Space Flight Center. Technical assistance from the SDAC is recommended in using these data.

Ancillary Data Information

Detailed knowledge of the instrument's pointing state is important to proper use of the data, and vital when comparing HXIS images with images from other sources.