File: SEL_M_071020_081226_SGMI_05.BSP

This SPICE kernel contains the orbit for the Main
satellite of the Kaguya (SELENE) project, as processed
and determined at the National Astronomical Observatory
of Japan, RISE Project. The start and end times of
the orbit are (in UT)

Start: 2007.10.20 00:00:00.00
End  : 2008.12.26 04:30:00.00

The gravity model used in the processing was SGM100i,
which is the current latest gravity field model based
on SELENE and historical tracking data (see Goossens et al.,
J. Geod., 85, 205-228, 2011, doi:10.1007/s00190-010-0430-2).
This model is based on the processing of the SGM100h model 
(see Matsumoto et al., J. Geophys. Res., E06007, 2010,
doi:10.1029/2009JE003499), with the difference
that SGM100i also includes all S-band same-beam VLBI
tracking between the sub-satellites.

The orbit of the Main satellite was determined using
available 2-way (range and Doppler) tracking, 4-way
tracking between the sub-satellite Rstar and the Main
satellite, and VLBI tracking between the sub-satellites
Rstar and Vstar. In addition, laser altimeter crossovers
were also used in the orbit determination for the months
January and March 2008 (see Goossens et al., J. Geod., 85, 
487-504, 2011, doi:10.1007/s00190-011-0446-2). 
Overlap analysis showed that including the crossovers 
reduces the orbit differences. It was also found that for 
some arcs in February, 2008, the orbit differences increased 
slightly when crossovers were included, so this version of 
the orbit kernel used no crossover data for arcs in February.

Crossover statistics per month:

Jan 2008: 13571 CROSSOVERS, RMS: 23.61 m
Mar 2008: 12544 CROSSOVERS, RMS: 23.47 m

Orbits are determined with arc lengths of in general
12 hours (6 hours after July 23, 2008 because of an issue
with one of the reaction wheels). The arcs are limited 
because of angular momentum desaturation events. The arcs 
are cut around these events, resulting in an orbit that is 
not connected.


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File: SEL_M_071020_090610_SGMH_02.BSP

This SPICE kernel contains the orbit for the Main
satellite of Kaguya, as computed at the National
Astronomical Observatory of Japan, RISE Project.

Start: 2007.10.20 02:30:00.00 UT
End:   2009.06.10 19:30:00.00 UT

Coordinate system during orbit determination: DE421
Based on the SGM100h gravity model (see Matsumoto et al., 
J. Geophys. Res., E06007, 2010, doi:10.1029/2009JE003499),
for orbits until 2009.02.12, 13:40:00.00 UT. After that, for the 
low-altitude part, the gravity field was LP150Q.

Data used were two-way data only. No 4-way data were used
in the orbit determination, but they were used in the
determination of the gravity field model (except of course
for LP150Q).

Per special request, this kernel consists of arcs
(continuous time spans used for processing the tracking
data in batches) that are connected. That means that there
are no gaps between arcs, so this orbit is continuous,
time-wise. There are however some gaps during altitude
manoeuvres, and they are listed below. On top of that,
due to the nature of orbit determination, there are jumps
at the arc boundaries. Arc lengths were two days
for arcs until 2009.02.12, 13:40:00, and one day after that.
Unloading events were taken into account in the processing
by estimating constant empirical accelerations in three
orthogonal directions during unloading times. Data fit for
most arcs is around 0.5 mm/s for Doppler data, but the
unloadings do introduce extra effects in the processing, and
uncertainties in their magnitude and direction lead to
orbital errors. Overlap tests showed radial errors of 3 m
at least, with much larger outliers possible (see below).

For the low-altitude part, and data after Dec. 26, 2008, the
spacecraft was in thrustering mode. This is taken into account
here by estimating accelerations in two directions (along and
cross track, or in the transverse and normal direction). The
accelerations have a once-per-orbital revolution period, and
one constant in along-track is also included. This is needed
to keep the data residuals at a reasonable level, which works
quite well, but again due to uncertainties, the orbit is much
less precise during this period.

The last arc, 2009.06.10 14:00 - 19:30, is not trustworthy,
since we lack information about thrustering to manoeuvre the
spacecraft into its final orbit. As a result, our orbit does
not crash.

----- Gaps due to altitude manoeuvres -----

The spacecraft was three-axis stabilised and its altitude was
maintained by doing periodical correction manoeuvres. According
to the Mission Working Group Meeting documents, mission instruments
were turned off during these manoeuvres. Since it is difficult to
do precise orbit determination without good thrustering information
during these events, the processing was stopped, resulting in some
gaps in the orbits. The times of the gaps are:

07.12.11 02:30 - 16:50
08.02.04 20:30 - 08.02.05 04:15
08.03.29 16:30 - 08.03.30 00:15
08.05.24 15:00 - 20:43
08.07.16 07:30 - 15:30
08.09.10 05:30 - 13:30
08.11.03 00:30 - 09:00
08.12.26 21:00 - 08.12.27 05:30
09.02.20 20:00 - 23:45
09.03.19 18:00 - 22:00
09.04.16 19:00 - 21:30