The first version of the long-awaited RHESSI roll aspect data base is now available on ATEST.

This database contains the mission-long RHESSI roll solution tabulated at 64s intervals.  
The new software on ATEST
defaults to using this database instead of calculating a custom PMTRAS roll solution for
each analysis.  The main advantage of 
this is the (hopeful) elimination of the star identification problem 
which occasionally gave incorrect roll aspect.  Secondary benefits are 
that the roll solution is faster, more accurate, more consistent, and will support 
more complete flare location lists,
extensive self-calibration of the PMTRAS system and long integration 
intervals for non-solar applications.

The initial posted database covers only February through May 2002.  
A larger version covering  
through 31 July 2003 has been generated and will be posted in a few days if there are
no reported problems with the initial period.  The database will be updated regularly
thereafter to incorporate more recent data. It currently requires about 1 Mbyte
per month, although this should be significantly reduced in future.

Although the roll database is over 90% complete, there are a large number of
individual gaps due to the absence of PMTRAS data,
points with lower quality solutions, and cases where data were acquired under 
'unusual circumstances' (such as periods of offpointing, spin-up, etc).
These gaps will be gradually filled in by nonlinear interpolation, custom PMTRAS analyses
and the use of CCD-RAS solutions.

The IDL log window will indicate whether the roll database is being used and will issue a warning
if there is are any potentially serious gaps in the roll solution at the time of your analysis.
If the roll database cannot be used at all 
for your interval, the software will automatically revert to
doing a custom PMTRAS solution as before.  In case of significant gaps (or any other reason),
you can override the use of the database by specifying the control 
parameter, as_roll_solution='PMT'.  For example: 
image_object ->set, as_roll_solution='PMT'		; when using the command line or
hessi, as_roll_solution='PMT'					; when starting the GUI.
(Other valid as_roll_solution arguments are 'RAS' or the default, 'DBASE'.)

Three PMTRAS-related logs are being maintained on http://sprg.ssl.berkeley.edu/~ghurford/roll_dbase/.
roll_dbase_gaps.txt is a time-ordered, machine-generated, but readable list of gaps in the current database.
roll_dbase_status.doc provides updates on the status of the roll aspect database.
pmtras_major_event_log.doc indicates 'major events' (excluding gaps) affecting PMTRAS performance.

The database (and the new version of PMTRAS_ANALYSIS on ATEST) also corrects a 1 millisecond 
timing error in all roll solutions obtained to date.  For all data acquired since 26 February 2002
the correction of this error
will rotate the absolute positions of all images by 1.5 milliradians clockwise 
about Sun center.  This corresponds to a position error on the Sun of
less than 1.5 arcseconds (worst case) except for  
the first 3 weeks after launch when the error
was 3 times larger. This error has had no effect on
spectroscopy, image morphology, image photometry,
or on 
relative positions
as a function of energy or time. 

Please let me know if  encounter any problems, suspect that
the roll database may be providing an incorrect solution for your time interval, have a particular 
gap that you would like filled ASAP or if you have any questions.

Thanks for your patience.

gordon hurford