Mis-identification of IGS Opt 5 R/B and IGS 9 R/B

From: C. Bassa via Seesat-l <seesat-l_at_satobs.org>
Date: Sat, 5 Nov 2022 13:28:54 +0100
It appears that the identifications of the objects that we have been
tracking as IGS Opt 5 R/B [40539/15015B] and IGS 9 R/B [40382/15004B]
are swapped compared to the identifications of the 18th SDS.

Both Japanese IGS satellites were launched during the winter of 2015
into the same sun-synchronous orbital plane; IGS 9 on
2015-02-15T01:21:00 and IGS Opt 5 on 2015-03-26T01:21:00 on H2A
rockets which left their rockets in orbit. The payloads and rockets
were first observed in April 2015, and it appears that at that point
their identifications were swapped.

As of November 4, a TLE has become available for IGS Opt 5 R/B from
space-track.org, and querying space-track.org reveals that orbital
elements of IGS Opt 5 R/B are now available dating back to June 18,
2015, some 3 months after the launch on March 26, 2015. The temporal
evolution of the orbital elements are consistent with those of a
non-manouvering orbit, which rapidly decayed from the start orbit of
465 x 484 km to altitudes dropping below 400 km in January 2022, below
300 km on October 8, 2022 and below 200 km on November
1st. Space-track.org has a 60 day decay message predicting decay on
November 3rd. The last TLE at November 2, 6:12UTC had a 129x143km
orbit, so it has decayed since.

Comparison of the IGS Opt 5 R/B TLEs from space-track.org shows that
it was mis-identified as IGS 9 R/B [40382/15004B], which we last
tracked in a 281x286km orbit on October 14. The IGS Opt 5 R/B TLEs
from around that date are an excellent match to the IGS 9 R/B
TLE. Comparison of the IGS 9 R/B elements from classfd.tle over the
past 7 years shows that our elements for IGS 9 R/B track the
space-track.org elements for IGS Opt 5 R/B extremely well. This
confirms that the objects were swapped when we first observed them.

I do not believe the identification of the payloads are swapped, as
the IGS optical and radar satellites use distinct orbital altitudes.

Regards,
   Cees
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Received on Sat Nov 05 2022 - 07:30:04 UTC

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