SatSpy and Mega-elset Files

Dave Cappellucci (dcappell@usa.net)
Fri, 15 Nov 1996 07:50:28 -0700

Hi All,

I've noticed several messages lately discussing problems in Satspy relating
to large element set files.  I ran some tests on both SatSpy 1.0 and SatSpy
2.0 using the largest files I could find (4892 elsets).  I ran both
programs on two different computers, an older 486DX-2 with 16M RAM running
Windows 3.1 and a newer P-133, also with 16M RAM, running Windows95.
Here's what I found:

1)  On the 486DX-2
  a)  V1.0 was able to load the full 4892 elsets and was able to compute
      multiple skytraces and most other observation tasks.  It failed 
      (rather ungracefully) when accessing the elset summary list.

  b)  V2.0 was also able to load the full 4892 elsets and open the elset 
      summary lists, but several of the dialog boxes using listboxes 
      could not be opened.

2) On the P-133 under Windows95:
  a)  V1.0 was able to load all elsets and process them successfully.

  b)  V2.0 was also able to load and process all of the elsets successfully.

The capacity problems that are being reported are due to the fact that
Satspy loads _all_ elsets into memory, rather than reading them from file
as needed.  This was a design decision dictated by my desire to make it as
easy and quick as possible to open  many different views on the same elset.
 Unfortunately, this also means that there is an upper limit, dictated by
machine type, available memory and choice of operating system (Win3.1x vs.
Win95 vs. WinNT), beyond which it becomes impractical to load every elset
in memory.  

So for those of you who need to load very large numbers of elsets, SatSpy
may not be the appropriate program (as it is currently designed).  I have
considered building a "Pro" version, built on database technology, which
would avoid this problem.  If this would be of interest to anybody, let me
know.

Thanks,

Dave Cappellucci (SatSpy author).

P.S. - For those of you who are registered users of SatSpy 1.0:  I recently
mailed (free) upgrades to V2.0 to my US customers.  You should have
received it already.  If not, let me know.  I will be shipping copies to my
non-US customers early next week.  For non-registered users, and anybody
else who might be interested,  I hope to post v2.0 (shareware) on my
website in the next few days.  (http://www.usa.net/acappella).