I have been looking around at the ways that various telescope pointing
systems obtain earth orientation data. A quick search around the web
reveals the following documents that describe semi-automated
techniques that use the information from Bulletin A:
http://sma-www.harvard.edu/private/memos/124.pdf
http://www.jach.hawaii.edu/JACdocs/UKIRT/UON/003/node18.html
http://www.apo.nmsu.edu/Telescopes/TCC/OperatorsManual.html#EarthOrientationPredictions
http://www.apo.nmsu.edu/Telescopes/TCC/Utilities.html#Utilities
http://www.alma.aoc.nrao.edu/development/computing/meetings/phonemeetings/2002-02-25.pdf
I have discussed this with colleagues elsewhere who also maintain
telescope pointing systems, and who have created similar schemes, but
they have not left documentation openly available on the web.
Therefore I suspect that there are many more instances of systems like
this.
These schemes are somewhat fragile. It would be interesting to know
how often a format change in Series 7/Bulletin A has caused them to
fail.
Even among those who most need to have an accurate value of Universal
Time (earth rotation), I suspect that there might be a consensus that
the current schemes for providing it are broken.
But distribution of the projected UT1 values is not the only scheme
that is difficult to parse. For an example, look at the way that NIST
distributes the information about how far UTC(NIST) differs from
UTC(USNO) and from UTC(the real one based on TAI); e.g.,
http://tf.nist.gov/timefreq/pubs/bulletin/pdf/2003JUL_TF_BULLETIN.pdf
http://www.bldrdoc.gov/timefreq/pubs/bulletin/pdf/2003JUL_TF_BULLETIN.pdf
I can't imagine trying to write a parser that could extract the
information from these tables in PDF files.
The result of the Torino meeting implies that we are going to be stuck
with UTC for another 20 years. That's a long time for a lot of time
users to have to update perl scripts or manually transfer data from
publications to operational systems. My impression is that many
programmers/system designers would find it difficult to believe
that these are serious efforts to distribute operational data in
the 21st century.
Shouldn't the astronomers, the atomic clock keepers, and the system
designers alike be demanding that IERS (BIPM, USNO), NIST and other
such agencies provide these data in more easily used formats?
Is anyone looking into providing these data as XML?
If not, who are the constituencies who should start writing to what
advisory bodies who could request that these agencies get out of the
19th century?
--
Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064
sla_at_ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla
PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93
Received on Thu Aug 14 2003 - 22:53:03 PDT