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sot / cheta

Cheta Telemetry Archive
https://sot.github.io/eng_archive
BSD 3-Clause "New" or "Revised" License
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Predictive Ephemeris Data Missing on 2000:071 #32

Open aarvai opened 12 years ago

aarvai commented 12 years ago

Predictive ephemeris data are missing from 2000:071:00:00:00 - 2000:071:12:03:56:00 UTC. This affects orbitephem0, lunarephem0, and solarephem0, as well as their associated MSIDs (_x, _y, _z, _vx, _vy, and _vz). Also, because of their dependence on ephemeris data, PCAD derived parameters DP_PITCH, DP_ROLL, DP_XZ_ANGLE are also affected. I believe this is the only time period in the current TLM archive with this issue (missing data for > 301 seconds). Definitive ephemeris is not affected.

For example:

In [57]: x=fetch.Msid('orbitephem0_x','2000:001')

In [58]: dt = diff(x.times)

In [59]: i = dt > 301

In [60]: Chandra.Time.DateTime(x.times[i]).date
Out[60]:
array(['2000:071:00:00:00.000'],
  dtype='|S21')

In [61]: Chandra.Time.DateTime(x.times[1:][i]).date
Out[61]: 
array(['2000:071:12:03:56.000'],
  dtype='|S21')

@taldcroft

taldcroft commented 11 years ago

I've confirmed this occurs in both the GRETA and HEAD versions. I tried re-ingesting the ephem0 data from the CXC archive and the same data gap appeared. Resolving this issue may not be easy, so it might be best to just set this as a bad time. Thoughts @aarvai?

aarvai commented 11 years ago

Since I believe that predictive ephemeris == definitive ephemeris for past data, an alternative approach would be to set the missing predictive values in the archive equal to the definitive values. I'd be comfortable with that from a data-fidelity standpoint. However, if that's too much trouble, setting it as a bad time is also fine. I don't believe there's anything historically significant about 2000:071, so I doubt the data will be substantially missed.