satellites/space segment

GPS Block IIF: A Third Cancellation
May 24, 2010

GPS Block IIF: A Third Cancellation

GPS IIF-SVN1: Still Waiting. United Launch Alliance photo

The third time wasn’t the charm for an attempted first launch of a GPS follow-on (Block IIF) generation of satellites.

Problems with ground support equipment and then with the telemetry signal between the spacecraft and the ground equipment have delayed initial launch of the new-generation satellite three times in the last four days.

Originally scheduled for May 20, the launch was postponed again on May 21 and May 23. Mission controllers hope to get the IIF off the ground on May 24.

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By Inside GNSS
GPS IIF Launch Scrubbed on Pad for Second Time
May 23, 2010

GPS IIF Launch Scrubbed on Pad for Second Time

GPS Block IIF-SVN1 on the launch pad at Cape Canaveral Air Force Station. United Launch Alliance photo

Launch managers canceled the second attempt to place the first GPS Block IIF satellite in orbit on Friday, May 21, when the telemetry signal between the spacecraft and the satellite ground support equipment was lost minutes before scheduled liftoff. The problem could not be resolved in time to launch during the 18-minute launch window. 

Another launch attempt has been set for Sunday, May 23, betwen 11:17 and 11:35 p.m. (EDT). The first launch effort on May 20 was called off when a problem with ground support equipment was detected during the day.

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By Inside GNSS
Equipment Problem Delays First GPS IIF Launch
May 19, 2010

Equipment Problem Delays First GPS IIF Launch

Boeing technicians examine the first GPS IIF satellite as it underwent final preparations for its February shipment to Cape Canaveral. Boeing photo

A ground equipment problem has caused a 24-hour delay in launch of the first GPS IIF satellite (GPS IIF-SV1).

Originally scheduled for late May 20, the launch attempt has been reslotted to a May 21 launch window of 11:25 to 11:43 p.m. (EDT)

During normal processing for the launch from Cape Canaveral, Florida, mission managers determined that a piece of ground support equipment used to control one of the swing arms on the fixed umbilical tower was not operating correctly and needed replacing.

Replacing the GSE component will add one day to launch processing, according to the United Launch Alliance managers. This will be the first launch of a GPS satellite on the Boeing Delta IV rocket.

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By Inside GNSS
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Space Weather Workshop Highlights Coming Solar Cycle Effects on GNSS
May 8, 2010

Space Weather Workshop Highlights Coming Solar Cycle Effects on GNSS

Solar Dynamics Observatory (SDO) spacecraft. NASA image

This year’s Space Weather Workshop — held April 27–30 in Boulder, Colorado — reflected a heightened interest in the space environment due to solar effects on GPS and other GNSSes. A solar storm is suspected to have caused the anomaly in Intelsat’s Galaxy 15 communications satellite that carries a transponder for the GPS Wide Area Augmentation System (WAAS),

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By Inside GNSS
U.S. Air Force Prepares First IIF GPS Satellite for Launch on May 21
April 19, 2010

U.S. Air Force Prepares First IIF GPS Satellite for Launch on May 21

A launch pad at Cape Canaveral (satellite image courtesy of GeoEye)

Launch of the first GPS Block IIF (follow-on) satellite is currently scheduled for May 21 from Cape Canaveral aboard a Delta-IV Evolved Expendable Launch Vehicle (EELV), with a destination in the constellation’s B2 plane and slot.

The IIF-1 SV (space vehicle) is at the launch site and fueled. A final IIF launch mission dress rehearsal (MDR) was scheduled to take place during the weeks of April  26 to May 7.

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By Inside GNSS
GAGAN Delayed Again
April 17, 2010

GAGAN Delayed Again

ISRO GSAT-4 satellite

India’s first GPS/SBAS payload, the GAGAN (GPS-Aided Geo-Augmented Navigation system) transmitter on the GSAT-4 geostationary satellite, disappeared into the Bay of Bengal on April 15 when its ill-fated GSLV-D3 launch vehicle veered off course.

The Indian Space Research Organization’s GSAT-4 satellite carried a communication payload of multi-beam Ka-band pipe and regenerative transponder and a navigation payload in C, L1 and L5 bands.

A key part of India’s GPS augmentation plan, the failure will further delay civil aviation modernization.

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By Inside GNSS
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EC Liberates Galileo ICD Signal Specification
April 14, 2010

EC Liberates Galileo ICD Signal Specification

Today’s (April 13) release of an updated “Galileo Open Service Signal-In-Space Interface Control Document” (OS SIS ICD) freed the key specification document in two senses of the word: receiver manufacturers, application developers and service providers may now use the ICD as an official — not draft — guide to their work, and they may do so at no cost

The t’s have been crossed and the i’s dotted to the satisfaction of lawyers and politicians — and the relief of designers and system integrators eager to begin work on Galileo-capable products without fear of having substantive changes in the specifications and legal or financial difficulties for moving ahead.

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By Inside GNSS
FAA Predicts Erosion of GPS WAAS Service Due to Intelsat GEO Failure
April 13, 2010

FAA Predicts Erosion of GPS WAAS Service Due to Intelsat GEO Failure

Galaxy 15 satellite under construction. Orbital Sciences photo

[updated April 13] Federal Aviation Administration (FAA) officials say that loss of control over an Intelsat geostationary (GEO) carrying a GPS Wide Area Augmentation System (WAAS) transponder could subject users in the National Air Space (NAS) to temporary outages for the rest of this year, beginning within the next two to four weeks as the GEO drifts out of a useable orbit.

Intelsat S.A. announced the anomaly in Galaxy 15 (G-15) on April 8. Although the communications services provided by G-15, located at 133 degrees west longitude (WL), have not been affected, according to Intelsat, the satellite apparently is not responding to commands by controllers. The anomalous condition began on April 3, according to the FAA.

The Luxembourg-based Intelsat is moving an older spacecraft (G-12) that serves as a backup for G-15 from its location at 123 degrees WL. However, G-12 does not have an L-band transponder, which is needed for WAAS transmissions.

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By Inside GNSS
U.S. Invites Comments for Easing GPS SVN49 Signal Anomaly
April 10, 2010

U.S. Invites Comments for Easing GPS SVN49 Signal Anomaly

(This article first appeared in the March 31 Inside GNSS SIGNALS eNewsletter)

The GPS Wing is in the middle of a yearlong process designed to sort out the trade-offs among a set of at least nine options that may be undertaken to reduce the effects of a signal anomaly on the GPS satellite known as SVN49.

In a March 26 teleconference, the first of two scheduled to discuss the options, Lt. Col. James Lake, the wing’s deputy chief engineer, emphasized that some of the options could well improve the performance of some receivers while decreasing that of others.

He underlined the Air Force’s concern that receivers that don’t conform to the specification for GPS space segment/navigation user interfaces (IS-GPS-200) "greatly complicate the issue."

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By Inside GNSS
European Space Weather Week 2010
March 29, 2010

European Space Weather Week 2010

Solar flare (NASA)

The 7th Space Weather Week will take place at Congress Centre Oud Sint-Jan in Bruges, Belgium from November 15 to 19 2010. The purpose is to bring the various countries and institutions of Europe together on space weather issues that concern them all.

It is organized by the European Space Agency, the Royal Observatory of Belgium, the Solar-Terrestrial Center of Excellence, and the European Commission COST office.

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By Inside GNSS
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