This is the TRACE Analysis Guide (TAG). The Guide is in two main parts, the TRACE Users Guide (Section 2) and the TRACE Instrument Guide (Section 3). The User Guide describes how to analyse TRACE data and the Instrument Guide discusses aspect of the TRACE instrument. Additional information is provided in the Appendices.
TRACE is a NASA Small Explorer (SMEX) mission designed to investigate the connections between fine-scale magnetic fields and the associated plasma structures on the Sun. The instrument collects images of solar plasmas from 104 to 107 K, with one arc second resolution and excellent temporal resolution and continuity.
The TRACE spacecraft was launched on April 2, 1998 (UT) into a Sun-synchronous (98°) orbit of 600×650 km. The baseline mission duration was 1 year. Its orbit allowed continuous observations of the Sun to be made for 7 months before entering an eclipse season of 3 months. Each subsequent year of operation will have a 9 month (mid February to mid November) non-eclipse season. TRACE is operated in coordination with SoHO from an Experimental Operational Facility (EOF) at GSFC, close to the SoHO EOF.
The 30 cm aperture TRACE telescope uses four normal-incidence (NI) coatings in quadrants on its primary and secondary mirrors. Observations are made at several UV and EUV wavelengths, selected using a sector wheel and two filter wheels. A Lumogen-coated 1024×1024 CCD collects images over a 8.5×8.5 arcminute field of view. The images are coaligned and internally stabilized against spacecraft jitter. See the Instrument Guide (Section 3) for more information about the instrument.
The TRACE instrument produces a lot of data - it has been averaging just over 3 GBytes per week. The TRACE instrument data are blocked into hour-long FITS files which have names of the form `` triyyyymmdd.hh00'', where ``tri'' is the prefix for the reformatted files, and ``yyyymmdd.hh'' is the start time of the file. The files contain in-line JPEG compressed images, as downlinked from the spacecraft. They need to be decompressed before the data can be used - this is done automatically by the analysis routine read_trace using the shared object binary trace_decode_idl.so.
The data files are normally stored under directories that hold a weeks worth of files and have names that correspond to the date of the starting day of the week, i.e. ``weekyyyymmdd'' where ``yyyymmdd'' is the week start date. The directories are addressed in the analysis software through the environment variable $TRACE_I1_DIR.
If data are requested from the TRACE DATA CENTER, the Multiple eXtension FITS (.mxf) files that are returned cover a specific time interval, and contain images that are already decompressed. The name of this file has the form `` trbyyymmmdd_hhmm.mxf'', where ``trb'' is the prefix of the file, and ``yyyymmdd_hhmm'' is its start date and time. As with the hourly tri files, the .mxf files can be read using read_trace.
Detailed TRACE analysis need certain ancillary data files, including the dark current files (tdc files). What observations have been made by TRACE can be determined from the catalog files (tcl, tcs and tce). The location of the spacecraft, etc. can be found from the ephemeris files (fdss_*). These files are all held under directories addressed through the environment variable $tdb and are normally distributed within the SolarSoft database tree ($SSWDB or /sdb) - see Appendix C for more information.
The TRACE DATA CENTER allows the user to request data based on entries in the TRACE Data Catalog. There are other ways of searching for particular TRACE data - these are detailed in Appendix B.3, and include:
TRACE Investigation and Technical Plan (Phase III & IV), August 1994, LMSC P017270P-1.
``The Transition Region and Coronal Explorer (TRACE)'', 1994, Tarbell et al., Estes
Park proceedings.
``The Transition Region and Coronal Explorer'', 1999, Handy et al., Sol. Phys., 187, 229.
``Data Analysis with the SolarSoft System'', 1998, Freeland and Handy, Sol. Phys., 182, 497.
Alan Title (LMSAL) title@lmsal.com Jake Wolfson (LMSAL) wolfson@lmsal.com Ted Tarbell (LMSAL) tarbell@lmsal.com Karel Schrijver (LMSAL) schryver@lmsal.com Dick Shine (LMSAL) shine@lmsal.com Sam Freeland (LMSAL) freeland@lmsal.com Rich Nightingale (LMSAL) ngale@lmsal.com Leon Golub (SAO) lgolub@cfa.harvard.edu Ed DeLuca (SAO) deluca@cfa.harvard.edu Brian Handy (MSU) handy@physics.montana.edu Charles Kankelborg (MSU) kankel@physics.montana.edu