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The System: Compass Signal ICD this Month

October 1, 2011  - By

The long-awaited signal interface control document (ICD) for China’s growing GNSS will appear this month, according to representatives of the system who spoke in a “Compass: Progress, Status, and Future Outlook” workshop as part of ION GNSS and the CGSIC meetings in Portland in September.

The ICD has been rumored to be available previously to receiver manufacturers within China, creating some disgruntlement among companies outside the country. One of the workshop panelists affirmed that GPS/Compass chips and receivers are being actively developed by many Chinese manufacturers and research institutes.

The ICD announcement came among many valuable pieces of information presented during the pre-ION workshop, sponsored by the International Association of Chinese Professionals in Global Positioning Systems and chaired by Jade Morton, professor of electrical and computer engineering at Miami University, Ohio.

Xiancheng Ding of the Beidou Program Office described Compass as a demo system in transition to an operating navigation system. Two more satellites will launch in 2011, making a total of five new space vehicles this year,as part of a total “simple navigational system” of nine satellites that has been built up, and what is termed a test system over the Asia-Pacific region, to be complete by the end of the year.

Five more satellites will rise into orbit in 2012, and the system will gradually extend its coverage and improve its performance. Compass will start official regional service by the end of 2012, meeting user requirements in the Asia-Pacific region.

ICD document v1.0 will be published in 2011, and probably in the month of October. It will be available for international download on the Compass website (as yet without an English version).

There was some disagreement among panelists as to the final targeted number of satellites in the system: either 30, or 35. Subsequent comments indicated that much of the structure may still be under discussion. The impression given was very much of a dynamic system in formation and growing rapidly.

In a presentation on “Preliminary Results of GPS/Compass Integrated Positioning and Navigation,” Uanxi Yang of China’s National Administration of GNSS and Applications reported integrated navigation with a Unicore UB 240 Compass/GPS receiver with up to 9-centimeter accuracy, and also mentioned a Shanghai Huace Compass/GPS receiver. Some systematic errors in Compass positioning were reported, and attributed to the sparse satellite distribution currently.

Yang concluded with the exhortation, “Reasonable Wishes for Compass!” emphasizing the delegation’s desire to continue working diligently on, but with realistic expectations for, the new system.

Orbit Roundup

In other satellite news and debuts anticipated around the world:

GPS. Back-channel reports say the cesium clock aboard SVN-63, the second IIF satellite, is not functioning properly, and that this is at least one reason why the satellite, turned over to 2SOPS control on August 19, has not been set healthy to users.

[Correction: The September issue and mistakenly reported that SVN-63 had been set operational on August 23. This is not the case. As of September 29, the satellite is still not healthy to users.]

After repeated attempts to get the clock working, operators are ready to switch to a rubidium clock onboard, and may already have done so.

GLONASS. The launch of GLONASS-M No. 42 from Plesetsk is scheduled for October 1. GLONASS-M Nos. 43, 44, 45 from Baikonur may occur as early as November 2. GLONASS-M No. 46 from Plesetsk is now scheduled for November 22. The launch of the next-generation GLONASS-K1 No. 12 from Plesetsk will likely slip to 2012.

The K1 satellites will not be set healthy, but held in reserve only. The remaining M-generation vehicles launching this year will fill up the 24 almanac slots. GLONASS will have plenty of satellites held in reserve.

Luch-5A, a Russian geostationary communications satellite that includes an SBAS payload, will launch on December 10 from Baikonur.

FCC Calls for More Testing on LightSquared Interference

The U.S. Federal Communications Commission (FCC)issued a Public Notice on September 14 stating that additional testing is necessary to ensure that LightSquared’s broadband network will not interfere with GPS.

The notice states: “Following extensive comments received as a result of the technical working group process required by the International Bureau’s Order and Authorization dated January 26, 2011, the Federal Communications Commission, in consultation with NTIA, has determined that additional targeted testing is needed to ensure that any potential commercial terrestrial services offered by LightSquared will not cause harmful interference to GPS operations….

“For more than three months, the technical working group, comprised of more than 120 participants including representatives from the Department of Defense, Department of Transportation and other federal agencies, the GPS community, various telecommunications companies and LightSquared, conducted an extensive set of tests, and LightSquared submitted a final report on June 30, 2011. The technical working group effort identified potential for harmful interference from LightSquared’s originally proposed deployment based on operation of terrestrial transmitters in both the upper and lower 10 MHz portions of its spectrum. The FCC issued a public notice on June 30, 2011, seeking comment on the report.

“LightSquared submitted proposed mitigation techniques to remedy the interference to GPS simultaneously with the technical working group final report. Notably, LightSquared proposed to revise its planned deployment to operate terrestrial transmitters only in the lower 10 MHz of its spectrum. The results thus far from the testing using the lower 10 MHz showed significant improvement compared to tests of the upper 10 MHz, although there continue to be interference concerns, e.g., with certain types of high precision GPS receivers, including devices used in national security and aviation applications. Additional tests are therefore necessary.”

Galileo Counts Down to October 20 for First Validation Satellites

The first flight of a Russian rocket, Soyuz, from Europe’s spaceport in French Guiana will carry the first two satellites of Europe’s Galileo navigation system into orbit on October 20, and the European Space Agency is reporting on the preparations.

The Soyuz launcher will be rolled out horizontally to the launch pad on October 14 and raised into its vertical launch position. The upper composite, comprising the Fregat upper stage, payload and fairing, will then be hoisted on top of Soyuz.

The two Galileo satellites arrived from the Rome facility of Thales Alenia Space Italy, also in mid-September. In 2012, a second pair of satellites will join them in orbit, with the task of proving the design of the Galileo system in advance of the other 26 satellites. The four satellites, built by a consortium led by EADS Astrium Germany, will form the operational nucleus of the full Galileo satnav constellation. They combine reportedly the best atomic clock ever flown for navigation — accurate to one second in three million years — with a powerful transmitter to broadcast precise navigation data worldwide.

The first Soyuz to rocket up from a port outside Baikonur in Kazakhstan or Plesetsk in Russia, the launch will take place from a new facility 13 kilometers northwest of the Ariane 5 launch site. French Guiana is much closer to the Equator than other launch possibilities, so each Galileo effort will benefit from the Earth’s spin, increasing the maximum payload into geostationary transfer orbit from 1.7 tons to 3 tons.

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