HESSI IMAGING IN PRACTICE

E. J. Schmahl, GSFC, U Maryland

Presented at the HEDAW, SSL, UC Berkeley, 28 February, 2001

1. USER-CONTROLLED PARAMETERS
   • Subcollimator Selection
     • Default Back Projection
     • Collimators too fine
     • Collimators too coarse
   • Map Location Problems
     • Strong external subsource
     • Source not in field
     • Map contains spin axis
     • Map contains mirror source
   • Map Pixel Problems
     • Pixels too large
     • Pixels too small
   • Time span
     • Too long
     • Too short

2. DIFFICULTIES AT THE SOURCE
   • Low Count rates
     • Source misidentification
     • Imaging non-convergence
     • Indeterminacy
   • Source Variability
     • Source variations during rotation
     • Source flux changes
   • Source Complexity
     • Extended sources
     • Mixed broad and narrow subsources
     • Multiple sources
   • Background
     • Large background
     • Variable background

3. PROBLEMS AT THE PC LEVEL
   • Hardware limitations
     • CPU speed
     • Memory
     • Disk space
     • Poor network connectivity
   • Software Limitations
     • SSW out of date
     • IDL path errors
     • Software bugs
     • Undocumented features & changes
     • Documentation

4. PROBLEMS AT THE SPACECRAFT LEVEL
   • Unpredictables
     • Detector noise, variability
     • Livetime << 1
     • SAS, RAS errors
     • Out-of-range pointing excursions
   • Correctables
     • Detector-to-detector sensitivity
     • Relative collimator phases