System of Systems: Second QZSS Signal on Air

August 16, 2017  - By
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QZS-2 L-band spectra, July 18, 2017, Weilheim, Germany. (Courtesy DLR)

Second QZSS Signal on Air

The successful launch of the Michibiki No. 2 satellite of the Quasi-Zenith Satellite System (QZSS) on June 1 has been followed by broadcast initiation. Researchers at the German Aerospace Center, Deutsches Zentrum für Luft- und Raumfahrt (DLR), have been observing the satellite from their ground station in Weilheim. They will provide a written analysis in the September issue.

The Japan Aerospace Exploration Agency launched first Michibiki satellite of the anticipated four-satellite constellation in September 2010.

Air Force to Recompete GPS III Follow-on

The U.S. Air Force will launch multibillion-dollar competition between current GPS III contractor Lockheed Martin Corp. and former GPS Block I and Block II contractor Boeing Co. for as many as 22 new GPS III satellites. At press time, an industry day in was scheduled for July 20 in El Segundo, California, to solicit company input, according to a new draft Request For Proposals.

In 2015 the Air Force undertook the first phase of a now two-year process to determine whether to put the next block of satellites up for competition. An initial review “has determined that viable, low-risk, high-confidence sources exist to conduct a full and open competition” for a second phase starting in fiscal 2018, according to the draft.

Lockheed Martin is assembling the first 10 satellites of the Block III program. Formal delivery of the first satellite was scheduled earlier this year, delayed by of a series of now-resolved problems with the navigation payload, cracked capacitors and a subcontractor gaffe last year that resulted in the wrong part being tested.

The satellite, which passed all of its qualification testing and verification, has been placed in storage pending the results of an unrelated review of the propulsion systems used to boost military satellites into orbit. The plan remains to launch the first GPS III satellite by spring of 2018.

“Lockheed Martin is working closely with the Air Force on resolving any concerns about the mission readiness of SV01’s Propulsion Subsystem,” Eschenfelder said in February. “We are confident that this review will not delay the Air Force’s planned spring 2018 Initial Launch Capability (ILC).”

NAVIC Clock Failures Resemble Galileo’s

The seven orbiting satellites of the Navigation Indian Constellation (NAVIC, formerly India’s Regional Navigation Satellite System, or IRNSS) have been hit by problems with some of their rubidium atomic clocks, similar to difficulties encountered earlier by Europe’s Galileo program.

NAVIC G-1 launch April 2017.

The Indian Space Research Organization (ISRO) had announced in July 2016 that all three atomic clocks on IRNSS-1A, launched in 2013, had malfunctioned, rendering that satellite ineffective.

Now, reports indicate that four more atomic clocks on the other six satellites launched more recently are not performing as required.

ISRO plans to launch a replacement satellite called IRNSS-1H in July-August to compensate for the loss of IRNSS-1A, although it is yet to announce the failure of more atomic clocks, which has not incapacitated the clock systems on the other six satellites.

The European Space Agency reported in January that anomalies had occurred in three of 36 Rubidium Atomic Frequency Standard (RAFS) clocks in the 18-satellite Galileo system, although none of the satellites were affected. ESA had said, “These failures all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground.”

ISRO has nine satellites indented for IRNSS. While seven satellites make up the Indian regional navigation constellation, the other two were indented as backup in the event of failure. Each satellite has three atomic clocks, one the primary timekeeper and the other two acting as backup.

“Measures are being taken to correct the problems caused by the clocks in the launch of future satellites. The atomic clocks to be used in the other satellites have been modified to prevent malfunction,” a senior official in the programme said.

ISRO chairman Kumar has indicated the number of satellites could go up from the originally envisaged seven to 11 but it is not clear if this is a consequence of the failing clocks. “We are set to launch more navigational satellites. They are in the process of approvals and clearances,” he said recently, and added efforts were on to revive the IRNSS-1A clocks.”

In Europe, the European Space Agency and an industrial partner-supplier have agreed that “some refurbishment is required on the remaining RAFS clocks” to be used in new Galileo satellites.

Look to GSA Service Centre for Galileo Advisories

In July, a wide transfer of responsibilities for the Galileo constellation took place, from the European Space Agency (ESA) to the European Global Navigation Satellite System Agency (GSA) of the European Union. Key among these was a handover of communications responsibilities to manufacturers, users and markets.

All parties can now find updates in the form of Notice Advisory to Galileo Users (NAGUs) at the GSA’s Galileo Service Centre, www.gsc-europa.eu/system-status/user-notifications.

NAGUs are issued as new satellites are launched and when satellites become ready for service provision, or to give advance warning of signal unavailability owing to planned maintenance or testing activities, or to notify users of unplanned outages and then to inform them when satellites become active again.

“Keeping our users in the picture on planned activities that might lead to satellite unavailabilityhas helped them to plan their own test activities and to prepare future products,” said Rafael Lucas Rodriguez, ESA’s Galileo services engineering manager.

A total of 189 NAGUs were issued under ESA oversight in the last four years, as the constellation grew to its current 18 satellites. The user base increased from 86 to 774 registered users on the European GNSS Service Centre website as companies worked to prepare Galileo-ready products. In December 2016, Galileo’s Initial Services began operating.

One regular consumer of Galileo NAGUs, Broadcom, uses them to organize engineering activities and tests as well as input them into its orbit prediction engine for its Long Term Orbits products.

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