Currently, the only way to determine the spacecraft spin period is to use the data from the Photomultiplier Roll Angle System (PMT RAS). For the demonstration flare, you must enter the following command in the IDL command line:
pmtras_analysis,'hsi_20020220_104040_002.fits',/NO_STARID
This runs a program written by Gordon Hurford that analyzes the PMT RAS data and outputs a plot of the spin period vs. time for the duration of the data in the fits file - hsi_20020220_104040_002.fits. Once you enter this line, you should see the following lines in the IDL window:
hsi_rd_pmtras: 64 packets of apID 154 were found.
PMTRAS_ANALYSIS: 1819 valid blips found between t= 0.000000 and 86400.0
PMTRAS_PERIOD_ESTIMATOR: Average period =4.332778 +- 0.000585 s
Also, the following plot should appear in a new window:
You must then read the spin period from the graph for the time of the flare. For the demonstration flare at 11:06 UT or 1440 s after the plot start time of 10:41:43.361 UT, the spin period is 4.3329 s.
For other time periods, you need to find out the name of the file that
contains the data to include in the command line above. This can be done by going to the site that you are using to
access the flight data and listing all of the files for the particular day of
interest. Data files for each day of the mission are stored in a directory tree using
the year, month, and day as subdirectory names. Note that the file name is
hsi_yyyymmdd_hhmmss_vvv.fits
where "hsi" identifies it as RHESSI data, "yyyymmdd_hhmmss"
is the year, month, day, hour, minute, and second, and "vvv" is the version
number of the file.
Find the file with data that covers your period of interest and enter its full name in place of the file name for the above pmtras_analysis program command line.