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Latest GPS Satellite Set to Healthy
http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=483301
Jan 9, 2008
GPS World
The U.S Coast Guard's Navigation Center (Navcen) confirmed that the GPS
IIR-18 (M) launched from Cape Canaveral December 20 was set to healthy
on January 2.
The satellite, dubbed SVN57, joins the four IIR-M satellites and 12
operational IIR satellites currently in the GPS constellation, which
comprises 31 operational satellites overall. GPS IIR-18 (M) will be
replacing SVN36, which in turn will replace SVN37, and be placed in
orbital slot C1, according to the U.S. Air Force. The orbital
initialization progress from the time of launch breaks down like this
(in reverse chronological order; provided by the U.S. Air Force):
o 2 Jan 21:00Z -- SVN57 was set healthy to users today at 20:41
Zulu (Z). All subsystems continue to operate nominally.
o 26 Dec 21:00Z -- The navigation payload initialization was
successfully accomplished today. The time line of events include:
o L1 transmitter on at 17:54Z
o L2 transmitter on at 17:55Z
o confirmed monitor station tracking at 18:24Z
o completed legacy signal adjustments at 19:57Z
o L2C on at 20:41Z
o M code on at 20:46Z
o Projected date for setting the space vehicle (SV) healthy to
users is 2 Jan. The NDS payload will be initialized 14:00-18:00
Jan 08.
o 24 Dec 00:00Z -- The clock and MDU have both been turned on and
all telemetry looks nominal. A passive support has been
accomplished by AEP to validate they could receive telemetry
prior to hand-off. The LADO operations are wrapped up and 2SOPS
will take over shortly.
o 23 Dec 20:30Z -- Solar array deployment was successfully
accomplished at 19:01Z. After successful three-axis transition,
sun acquisition was initiated. Sun search hold was completed at
19:25Z. This mission experienced the quickest Earth acquisition
to date, with sun nadir pointing occurring at 19:42Z. The NAP
antenna was deployed at 19:51Z and the W sensor antennas were
successfully deployed at 19:55Z. All SV subsystems remain
nominal. The next events are SPU drift configuration, redundancy
management configuration, and power management configuration. The
plan is to complete clock and MDU initialization this afternoon
and hand off the SV (space vehicle) to AEP. 2SOPS will monitor SV
state of health via AEP for the next two days and then we will
conduct nav payload initialization on the 26th.
o 23 Dec 09:30Z -- The 51-10 rpm despin initiated at
approximately 08:16Z with a burn duration of 22 minutes and
resulted in a final spin rate of 9.77 rpm. The 10-1.3 rpm despin
initiated at approx 09:00Z with a burn duration of 5 minutes and
resulted in a final spin rate of 1.26 rpm. The next major event
is the deployment of the solar arrays scheduled for 19:20Z. The
clock and MDU turn on times have been moved up to approx 22:00Z
on 23 Dec. All SV subsystems, as well as the control segment, are
performing nominally.
o 23 Dec 07:00Z -- Final orbit analysis indicates a post AKM
drift rate of -.9765 deg/day (West) which will result in an
on-station date of 16 Jan 08 in slot C1. Mission planers had
targeted a drift rate of -1 deg/day to allow time for another SV
to be repositioned starting on 8 Jan. The AKM efficiency was
99.9692 percent and the final inclination is 54.96 degrees. The
next maneuvers are the 51-10 despin scheduled for 08:20Z and the
10-1.3 despin scheduled for 09:10Z. The DRAM scheduled for 24 Jan
is canceled. All SV subsystems, as well as the control segment,
are performing nominally.
o 22 Dec 23:45Z -- Apogee kick motor (AKM) burn was successfully
initiated at 23:19.57Z. The burn time was nominal and all
telemetry indications show a good burn. The final orbit analysis
will be available in about 6 hours. All SV subsystems remain
nominal. Initial despin of the spacecraft will begin 23 Dec at
08:45Z.
o 21 Dec 23:30Z -- Trim 2 is canceled. All SV subsystems, as well
as the control segment, are performing nominally. The latest MES
is shown below.
o 21Dec 1630Z -- Although the CSPM burn, using the 5-pound
thrusters, was only planned to get the SV within 7 degrees of the
AKM targeting angle, we ended up only 0.86 degrees off. As a
result, a small TRIM1 was conducted at 15:30Z. The burn, using
the 0.2-pound thrusters, was 2 minutes and 6 seconds in duration.
The final Sun Z after the burn was 77.87 degrees compared to a
target of 77.89 degrees. The SV spin rate remained unchanged at
49.3 RPM. Attitude data will be collected over the next orbit to
determine if the second fine spin precession maneuver, currently
planned for 22 Dec 04:45Z, will be required. The AKM burn, which
will put us in our mission orbit, is still scheduled for 22 Dec
at 23:21.09Z. All SV subsystems, as well as the control segment,
are performing nominally.
o 21Dec 00:30Z -- CSPM was successfully executed on time at
23:31Z. The final Sun Z was almost perfectly on target at 76.85
degrees, compared to a planned 76.80 degrees. The SV spin rate
slowed slightly to 49.3 RPM, which is expected. All SV subsystems
remain nominal. Attitude data will be collected over the next two
orbits in preparation for the first fine spin precession maneuver
(TRIM1), which is currently scheduled for 21 Dec 15:30Z. TRIM 2
remains on its nominal time line at 22 Dec 04:45Z while the AKM
burn will move out 5 minutes to 22 Dec 23:21Z.
o 20 Dec 2230Z -- Mission GPS IIR-18(M) successfully launched at
20:04Z today, five minutes into the planned 14 minute launch
window. The five-minute delay was due to a collision avoidance
(COLA) restriction from the ISP. Six hours prior to launch, we
were notified that the Diego Garcia ground station was red and
may not be green for launch. Diego is not a mandatory asset for
launch but the loss of Diego ground station for our fine spin
precession maneuvers would have ultimately caused a delay in the
AKM maneuver from apogee 9 to apogee 13 and added risk to the
mission.
o The mission planners quickly conducted a re-plan of the mission
using LION and BOSS (ground stations for the TRIM) maneuvers and
were able to hold AKM to apogee 9. As a result of the launch five
minutes into the window and the change in maneuver planning, all
maneuvers in the attached MES will likely change slightly.
Updates will be provided prior to each maneuver. The first
command was successfully sent from Schrieffer and received by
SVN57 at 21:24 Zulu.
o Our spin rate and Sun Z are as expected and all SV subsystems
are nominal at this time. The first SV maneuver will be the
coarse spin precession maneuver (CSPM) now scheduled for 23:31
Zulu.
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