Early Orbit Checkout Extended for IIR-20(M)

The following is a press release from Los Angeles Air Force Base.

Release Number: 020609

6/16/2009 - LOS ANGELES AIR FORCE BASE, Calif. -- The U.S. Air Force
is investigating the cause and effects of signal distortions observed
from the GPS IIR-20(M) spacecraft launched on March 24, 2009. Routine
early orbit checkout procedures determined that GPS IIR-20(M) signals
were inconsistent with the performance of other GPS IIR-M satellites.
The signal distortion was initially observed as an elevation-dependent
bias in ranging measurements from GPS monitor stations.

Worldwide GPS users are not affected since this satellite is still in
early orbit checkout and has not been introduced into the operational
constellation.

A dedicated response team of Air Force and contractor experts are
wrapping up their investigation of the cause. An extensive series of
on-orbit signal quality measurements and ground tests clearly indicate
that GPS IIR-20(M)'s observed behavior is related to the interface for
the L5 demonstration payload. The demonstration payload, which is
powered on and operating exactly as expected, successfully brought
into use the L5 International Telecommunication Union frequency
filing, ensuring the frequency allocation will be available to support
future L5 users.

The Air Force team has identified several parameters in the GPS IIR-20
(M)'s navigation message that can be adjusted to correct the bias and
bring the satellite into compliance with the GPS Performance
Standards. Over the next several months the team will be testing,
analyzing and evaluating any potential impacts the corrective actions
may have on both military and civil GPS user equipment. The test
strategy implements engineering analysis, modeling and simulation, and
testing of real-life GPS receiver equipment to the greatest extent
possible to ensure that there will be no inadvertent impacts to GPS
users.

The Air Force expects to complete testing around the October 2009
timeframe. GPS IIR-20(M) will be introduced as a healthy satellite
into the operational constellation at that time if no major issues are
observed during the receiver testing campaign. Users will be kept
informed of the status of GPS IIR-20(M) via standard Notice Advisory
to Navstar Users (NANU) messages.

The GPS constellation remains healthy, stable, and robust with 30
operational satellites. The Air Force has high confidence there is no
related concern with the remaining IIR vehicles or the upcoming GPS
IIR-21(M) mission. The Air Force is executing a nominal processing
flow for an August 2009 GPS IIR-21(M) launch opportunity.

The Air Force remains committed to ensuring a continued high level of
GPS service and capability, maintaining GPS as the premier provider of
positioning, navigation, and timing for military and civilian users
throughout the world.

The Space and Missile Systems Center, located at Los Angeles Air Force
Base, Calif., is the U.S. Air Force's center of acquisition excellence
for acquiring and developing military space systems including GPS,
military satellite communications, defense meteorological satellites,
space launch and range systems, satellite control network, space based
infrared systems, intercontinental ballistic missile systems and space
situational awareness capabilities.

The Wall street Journal had a different take:

Wall Street Journal, 06/17
NEW GPS SATELLITE GLITCH RAISES CONCERNS ABOUT ACCURACY: Technical
problems are degrading the accuracy of signals from the latest GPS
satellite launched by the Pentagon, sparking concerns among U.S.
military and aerospace industry officials that the next generation of
the widely-used satellites could face similar troubles. The Air
Force's Southern California space acquisition center on Tuesday
announced that a Global Positioning System satellite, manufactured by
Lockheed Martin Corp. and launched in March, is experiencing
performance problems in orbit. It hasn't become part of the
"operational constellation" of more than two dozen other GPS
satellites, and is slated to undergo a battery of tests expected to
stretch through October to try to resolve the problems, according to
an Air Force press release. The GPS system, which serves both military
and civilian users, provides precise time and location coordinates for
everything from military missile launches and "smart" bombs to
automated bank-teller machines to aircraft, ships and everyday
vehicles. The Lockheed satellite is the first to include a new
civilian frequency - dubbed L5 - designed for, among other things, use
by future nationwide air- traffic control systems. But that signal,
part of the test package, apparently is interfering with other signals
from the satellite and reducing their accuracy, according to industry
and Air Force officials. The degraded signals are accurate only to
about 20 feet, versus about two feet for typical GPS signals, industry
officials said. The issue is significant, according to these
officials, because it could complicate deployment of a new family of
Boeing Co. GPS satellites currently being built that also feature the
L5 signal. Concerns over signal quality come barely weeks after a
Congressionally-ordered study raised a red flag about potential
erosion of GPS accuracy in the next few years due to launch delays and
other challenges. The Pentagon responded by minimizing the potential
risk, arguing that significant spare capacity remains on orbit and on
the ground to handle unexpected problems.

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The party line from the wing is that it can be fixed. I am not so
sure. See
http://groups.google.com/group/sci.geo.satellite-nav/browse_thread/thread/3bd0f7b7ec7e7286/996b6bbae20c05f2?q=group:sci.geo.satellite-nav+author:n00spam%40comcast.net#996b6bbae20c05f2


October is an interesting target date for completing the analysis.
First, October is in the next fiscal year. Second, it is after the
OCX award. I wonder what is lurking under that rock? The JPL Kalman
Filter comes to mind but that is a different topic.

The Wall Street journal seems to be asking if near and far field
antenna testing has been done on the IIF bird. When I am asked by a
customer how much testing they need my response is always "how much
money do you have?". Then we get into a serious discussion. I am not
knocking the wing for not doing near and far field testing on IIR-20
(M) but they sure as heck better be doing it on the Block IIF now.

--Mike Jr