The next GPS satellite, Block IIF-3 (SVN65), scheduled to be launched on October 4, will be positioned in orbital slot 1, which is in plane A. This slot is currently occupied by a Block IIA satellite, SVN39, operating as PRN09. SVN39 is one of the oldest operating satellites in the GPS fleet, dating from June 1993. SVN65 will the the third of a projected 12 IIF satellites to attain orbit.
Galileo IOV Tandem in October, Too
The previously announced September 28 launch date for the second set of Galileo IOV satellites has reportedly been pushed back to October 10.
Meanwhile, after more than four years of service as a Galileo testbed satellite, GIOVE-B was retired on July 23. Its navigation transmitters were switched off, according to an announcement from the European Space Agency, and the satellite’s height was raised in a series of steps to a graveyard orbit where there will be no danger of it interfering with the operational Galileo satellites or other spacecraft.
The SES-5 geostationary communications satellite (also known as Sirius 5 and Astra 4B), launched in July, arrived at its orbital slot of 5 degrees east longitude late that month. The current position is actually about 5.2 degrees. The satellite carries L1 and L5 transponders for the European Geostationary Navigation Overlay Service (EGNOS) satellite-based augmentation system. The GPS Directorate has assigned C/A PRN code 136 and L5 PRN code 136 for use by the satellite.
GAGAN in September
India’s GSAT-10 telecommunications satellite — one of two passengers for Arianespace’s upcoming Ariane 5 mission on September 21 — has completed pre-flight preparations at the Spaceport in French Guiana. Aboard GSAT-10 is the GAGAN (GPS and GEO augmented navigation) payload, which will support the Indian government’s implementation of a satellite-based regional capability to assist aircraft navigation over Indian airspace and in adjoining areas. GSAT-10 is expected to be positioned at 83 degrees east longitude and use PRN code 128. It will join the first GAGAN-equipped satellite, GSAT-8, launched in May 2011, and now at 55 degrees east longitude and transmitting test signals on the L1 frequency using C/A PRN code 127. Although GSAT-8 reportedly carries a dual-frequency transponder, no L5 signals from this satellite have yet been detected by International GNSS Service tracking stations.
GLONASS SBAS in September as Well
Luch-5B, the second of three geostationary satellites to reactivate Roscosmos’s Luch Multifunctional Space Relay System, is scheduled for launch no earlier than November 1, 2012, to be positioned at 16 degrees west longitude. The system’s multi-functional satellites carry transponders for the System for Differential Correction and Monitoring (SDCM), Russia’s satellite-based augmentation system. The transponders will broadcast GNSS corrections on the standard GPS L1 frequency using C/A PRN codes assigned by DoD’s GPS Directorate.
Luch-5A, launched in December 2011, has been placed in an orbital slot at 95 degrees east longitude. It began transmitting corrections on July 12, using PRN code 140.
SVN49 Back on the Air, Unhealthy
The GPS Block IIR-M satellite, SVN49, briefly resumed transmissions as PRN24 on August 9. The signals were marked unhealthy and the satellite was not included in broadcast almanacs. SVN49 was launched in March 2009, but remains out of service until an L1/L2 satellite multipath issue is resolved. Although not in the almanacs, a number of stations of the International GNSS Service tracked SVN49. See http://gge.unb.ca/test/IGS_stns_tracking_G24_223.pdf. SVN49 stopped transmitting signals as PRN24 on August 22. SVN49 previously operated between March 28, 2009, and May 6, 2011, as PRN01, and between February 2 and March 14, 2012, as PRN24.
Beidou Begins Testing Network
China will build a Beidou testing and certification network over the next three years to sharpen the system’s global competitiveness, according to a statement from China’s Certification and Accreditation Administration. By 2015, a national testing center will be set up in Beijing, while seven local sub-centers will be established across the nation, it said. The centers will test the safety and accuracy of products designed for use with Beidou and qualify them for civilian use. China plans to launch 30 satellites to complete the system by 2020.
The launch of next two Beidou-2/Compass medium-Earth-orbit satellites, M2 and M5, did not occur in August as was previously speculated. A knowledgable source states: “All three active Chinese tracking ships have retreated to their home base Jiangyin, north of Shanghai. (Two ships are required for tracking down-range for a typical Chinese beyond-low-Earth-orbit launch.) The launch was put off for the remaining part of August and at least the first couple of weeks in September. The most recently speculated launch date is September 18.”
By Richard B. Langley, Simon Banville, and Peter Steigenberger.
For a brief period, and for a few hours on certain days, signals from the first four orbiting Galileo satellites could be received by state-of-the-art multi-frequency, multi-constellation GNSS receivers. Although not intended for actual positioning tests, the satellites did provide a first opportunity to assess the prototype Galileo signals in the positioning domain. The results obtained bode well for the future operational Galileo constellation.
The launch and successful operation of the two Galileo In-Orbit Validation Element (GIOVE) satellites — GIOVE-A and GIOVE-B — followed by the two Galileo In-Orbit Validation (IOV) satellites — ProtoFlight Model (PFM) and Flight Model 2 (FM2) — were important steps in the development of Europe’s Galileo satellite navigation system.
The GIOVE test-bed satellites were orbited to secure the use of the frequencies allocated by the International Telecommunication Union for the Galileo system; to verify the most critical technologies of the operational Galileo system, such as the on-board atomic clocks and the navigation signal generator; to characterize the novel features of the Galileo signal design, including the verification of user receivers and their resistance to interference and multipath; and to characterize the radiation environment of the medium Earth orbits planned for the operational Galileo constellation. The IOV satellites, of which there will be four with two more to be launched this fall, are prototype operational satellites designed to validate the Galileo concept in both space and on Earth. Once all four IOV satellites are in orbit, it should be feasible to carry out positioning exercises using just Galileo satellite signals. It was not intended for the GIOVE plus two initial IOV satellites to be used for positioning demonstrations. However, it turns out that (before GIOVE-A and GIOVE-B were recently decommissioned) for a few hours on certain days, signals from all four satellites could be received simultaneously by state-of-the-art multi-frequency, multi-constellation GNSS receivers.
Dual-frequency measurements from the GIOVE satellites and triple-frequency measurements from the IOV satellites have been archived by a number of continuously operating receivers including those in the COoperative Network for GIOVE Observation (CONGO) and those contributing to the International GNSS Service’s Multi-GNSS Experiment (M-GEX) observing campaign. Before joining the M-GEX campaign as the receiver at station UNB3 at the University of New Brunswick (UNB) in Fredericton, Canada, a Trimble Navigation NetR9 receiver fed by a Zephyr Geodetic II antenna was continuously tested at UNB for a couple of months and its 30-second-interval measurements were locally archived. These measurements included (in the terminology used by the Receiver Independent Exchange (RINEX) version 3 format): C1X, L1X, and S1X (pseudorange, carrier-phase, and carrier-to-noise-density-ratio measurements for combined data-plus-pilot tracking of the Open Service signal on the E1/L1 carrier frequency (1575.42 MHz)); C5X, L5X, and S5X (the corresponding in-phase and quadrature (I+Q) measurements on the E5a carrier frequency (1176.45 MHz)); C7X, L7X, and S7X (the corresponding I+Q measurements on the E5b carrier frequency (1207.140 MHz)); and C8X, L8X, and S8X (the corresponding I+Q measurements on the effective E5a+E5b carrier frequency (1191.795MHz)).
The first two of four Galileo IOV satellites were launched on October 21, 2011. Credit: ESA.
Although the IOV satellites are in synchronized orbits in the same plane with mean orbital periods of 1.70475 orbits per day, those orbits are not coordinated with those of the GIOVE-A and GIOVE-B satellites, which had mean orbital periods of 1.69434 and 1.70960 orbits per day, respectively. (The orbit of GIOVE-B was recently raised, following decommissioning.) This means that all four satellites will not generally be in view at a ground station at the same time. However, at a given location on certain days, four-satellite visibility did occur for periods up to a few hours. We identified several such days but were hampered in our efforts to obtain positioning solutions due to the testing programs of the satellites.
Our first constraint concerned GIOVE-A. The European Space Agency carried out tests with this satellite for more than six years and decided to decommission the satellite for its purposes on June 30, 2012, and switched off the navigation signals. This narrowed our window of possible four-satellite-visibility days. Secondly, the clocks on the IOV satellites were allowed to drift so that their offsets with respect to GPS System Time could be very large with offset values of tens to hundreds of milliseconds. Some GNSS receivers cannot make usable measurements when presented with such large clock offsets. This behavior further limited our windows of opportunity for four-satellite Galileo positioning. Nevertheless, we found that on May 17, 2012, the receiver at UNB successfully tracked the four satellites with a period of common visibility of two and a half hours. See Figure 1 for the time series of the occurrences of actual measurements made by the receiver. Common visibility extended from 03:04:30 to 05:34:30 GPS Time with the receiver tracking the satellites without any elevation-angle cutoff imposed.
In the remainder of this article, we describe the procedures used to obtain precise positions from the measurements, including the technique used to determine precise orbit and clock data for the Galileo satellites, and the results we obtained.
Figure 1. Visibility of Galileo satellites from UNB on May 17, 2012.
Generating the Orbits and Clocks
GIOVE and IOV satellite orbit and clock parameters are determined at Technische Universität München with a modified version of the Bernese GPS Software in a two-step procedure based on GPS and Galileo observations of 23 CONGO stations. After a common preprocessing step (detection of outliers and cycle slips), GPS and Galileo observations are treated separately. Station coordinates, tropospheric delay parameters and receiver clocks are obtained from GPS observations only. GPS satellite orbits and clocks as well as Earth rotation parameters from the Center for Orbit Determination in Europe (CODE) are kept fixed in this step. In the second step, the ionosphere-free linear combination of E1 and E5a observations is used to estimate the Galileo-related parameters, namely the satellite orbits and clocks. The station coordinates and the troposphere and receiver clock parameters are fixed to the GPS-derived results of the first step. To account for systematic differences between the GPS and Galileo code signals as well as biases between the different receivers, differential code biases (DCBs) are estimated for all stations but one. Separate biases are set up for the GIOVE and IOV satellites. To strengthen the stability of the orbital arc, five daily solutions are combined into a multi-day solution and consistent Galileo clock parameters are recomputed. Only the middle day of the5-day solution is used for the positioning discussed in this article. Based on internal consistency tests and satellite laser ranging residuals, the accuracy of these orbits is assumed to be on the one-to-two-decimeter level.
The Positioning Technique
A preliminary assessment of the quality of Galileo-only positioning could be achieved using the four satellites simultaneously in view at UNB. The second author’s GNSS positioning software was used to process the UNB data. Applying a 7.5-degree elevation cutoff angle to remove low-elevation-angle measurements resulted in an observation session of 1 hour and 48 minutes. The east or longitude dilution of precision (DOP) component starts out at 0.829 at the beginning of this session, gradually dropping to 0.688, and then rising to 1.285 at the end of the session; while the north or latitude DOP component starts out at 2.683 at the beginning of the session, rising to 4.233 at the end (see Figure 2).
Figure 2. North (N), east (E), vertical (V), and geometrical (G) dilution of precision (DOP) values.
Even though the receiver was tracking signals on E1, E5a, E5b, and E5a+b, carrier-phase and code observations on E1 and E5a were selected to match the satellite-clock datum. Ionosphere-free combinations were formed to eliminate first-order ionospheric effects, while the tropospheric delay was modeled using local measurements of temperature, pressure, and relative humidity provided by UNB’s meteorological station. No residual delay was estimated. Phase center offsets (PCO) and variations (PCV) for the Trimble Zephyr Geodetic II antenna were obtained through anechoic chamber calibrations (see Further Reading). The same satellite PCO as the ones used in the generation of the satellite orbits and clocks were applied, and no satellite PCV were considered. Other error sources required for precise positioning were also modeled such as solid Earth tides, ocean tide loading, and phase wind-up.
Since separate biases were set up in the estimation of the GIOVE and IOV satellite clock estimation, the same approach should be used on the user side. Unfortunately, solving for this additional parameter in the navigation filter is not possible when tracking only four satellites. To overcome this limitation, a GIOVE/IOV offset was estimated using 24 hours of combined GPS-plus-Galileo observations in static mode (one position solution for the whole observation period), and was introduced as an additional correction in the Galileo-only solution. The estimated coordinates from this combined solution were also used as a reference in computing the errors in latitude, longitude, and height presented next.
Results and Discussion
Three solutions were computed to demonstrate the quality of Galileo-only navigation. In the first scenario (see Figure 3), ionosphere-free code observations solely contributed to the epoch-by-epoch estimation of receiver position and clock offset. The estimated coordinates are largely contaminated by code noise, which is amplified by a factor of approximately three when forming the ionosphere-free combination. In the absence of redundancy, any errors in the observations (such as noise) propagate directly into the estimated quantities and, in this case, affected particularly the latitude component. An analysis of the noise and multipath characteristics of each signal revealed the presence of time-varying effects in the C5X observations. Further investigations are required to properly identify the cause of those effects. As a result, the root-mean-square (RMS) error of the latitude, longitude and height components were 3.084, 0.658 and 1.617 meters, respectively (see Table 1).
Figure 3. Code-based solution. Differences in latitude, longitude, and height with respect to reference coordinates.Table 1. Summary of the RMS errors for the three solutions computed.
As a second step, both code and carrier-phase observations were combined into a single adjustment (see Figure 4), yielding what is often referred to as precise point positioning (PPP). To accommodate the initial carrier-phase ambiguities, additional parameters were estimated in the filter. While adding carrier phases clearly reduces the noise in the solution, the estimated coordinates do not converge to cm-level accuracies, as typically expected in PPP. Despite weak geometry and range errors, the main reason for poor convergence is again the presence of biases in code observations. Without redundancy, carrier-phase observations only act as a filter for code observations, without reducing the contribution of biases. The RMS errors are 0.422 meters in latitude, 0.150 meters in longitude, and 0.389 meters in height.
Figure 4. Combined code and carrier-phase solution. Differences in latitude, longitude, and height with respect to reference coordinates.
To get an independent assessment of carrier-phase observations, a phase-only solution was computed (see Figure 5). For this test, a different methodology was adopted in which we simulated starting the positioning at a known precise location. At the first epoch, the receiver coordinates were constrained to the estimated values from the 24-hour GPS-plus-Galileo positioning solution, and the receiver clock offset was fixed to an arbitrary value (in this case zero). This initial epoch thus allowed estimation of the carrier-phase ambiguities, which remained constant for the rest of the session. For subsequent epochs, the receiver position and clock offset were estimated on an epoch-by-epoch basis. Even though the errors in the initial ambiguity estimates propagated into the following epochs, the estimated coordinates remained at the centimeter level throughout the nearly two-hour common observing period.
Figure 5. Phase-only solution, starting at a known location. Differences in latitude, longitude, and height with respect to reference coordinates.
Conclusion
We have obtained what we believe to be the first positioning results using observations from the four Galileo satellites launched to date. The results are very respectable given that the observing geometry was far from ideal and there was no redundancy for epoch-by-epoch solutions. Furthermore, the satellites were not operating at a performance level to be expected for the fully operational future constellation. Both GIOVE satellites have been retired and we must now wait for the second set of IOV satellites to be orbited before we can continue our investigations in Galileo-only positioning with live signals.
Acknowledgments
We thank the operators and station managers of the CONGO network for supplying the data used to model the orbits and clocks of the Galileo satellites.
Richard B. Langley is a professor in the Department of Geodesy and Geomatics Engineering at the University of New Brunswick (UNB) in Fredericton, Canada.
Simon Banville is a Ph.D. candidate in the Department of Geodesy and Geomatics Engineering at UNB. He is also working for Natural Resources Canada on real-time precise point positioning.
Peter Steigenberger is a staff member in the Institut für Astronomische und Physikalische Geodäsie of the Technische Universität München in Munich, Germany.
FURTHER READING
“Anechoic Chamber Calibrations of Phase Center Variations for New and Existing GNSS Signals and Potential Impacts in IGS Processing” by M. Becker, P. Zeimetz, and E. Schönemann, presented at the IGS Workshop, Newcastle upon Tyne, England, June 28–July 2, 2010. Available online: http://www.igs.org/event/newcastle2010/ (scroll to “0205” and click on “PDF.”)
“Precise Orbit Determination of GIOVE-B Based on the CONGO Network” by P. Steigenberger, U. Hugentobler, O. Montenbruck, and A. Hauschild in Journal of Geodesy, Vol. 85, No. 6, 2011, pp. 357–365, doi: 10.1007/s00190-011-0443-5.
China’s Beidou/Compass system will spur the country’s economic development in the satellite-navigation industry, geoinformation, and location-based services, according to an article in China Daily. China’s civil navigation providers are likely to experience rapid growth during the 12th Five-Year Plan (2011-15) period.
According to the article, “Earlier this month, Wang Chunfeng, deputy director-general of the National Administration of Surveying, Mapping and Geoinformation, said the government is likely to introduce policies to help the geoinformation industry grow.
“In addition, the nation’s self-developed satellite navigation network, the Beidou Navigation System, will come into commercial use by the end of this year, a move that may stimulate the development of the geoinformation industry in China.”
CSR plc has introduced the SiRFstarV 5t tracker, the first SiRFstarV architecture product optimized to deliver continuous, highly accurate location awareness to the latest generation of smartphones, tablets, and other mobile devices. The quad-GNSS SiRFstarV 5t tracker is the first SiRFstarV device to offer exclusive CSR adaptive continuous tracking power management technology, which CSR said offers significant power savings for extended battery life, and also includes MEMS inputs, LTE immunity, enhanced active jammer removal and other SiRFstarV features.
The SiRFstarV 5t is in use by LG Electronics for its first quad-core smartphone, the LG Optimus 4X HD, which takes advantage of the device’s GLONASS support and high sensitivity, CSR said.
“With GPS, GLONASS, Galileo, and Compass system capabilities, our new power-saving technology and the other SiRFstarV features, the SiRFstarV 5t tracker is perfect for mobile device OEMs looking to create new products that take location and navigation to the next level for an enhanced user experience,” said Dave Huntingford, director of location product line marketing at CSR. “We believe the SiRFstarV 5t again demonstrates CSR leadership in providing best-in-class location solutions that meet or exceed the demanding requirements of smartphone OEMs and operators.”
Optimized for size- and power-constrained applications, the SiRFstarV 5t boasts a number of enhanced SiRFstarV architectural features — from quad-GNSS support and MEMS-aiding, to improved sensitivity and interference rejection to small size and low BOM count — that result in location performance and power consumption improvements, reduced package size, easier integration and lower-cost implementation, CSR said. The SiRFstarV 5t supports A-GPS and A-GLONASS in MSA and MSB modes, and has been tested for all major carrier requirements, including SUPL1.0 and SUPL2.0, and offers improved 3GPP acquisition and tracking margins. SiRFInstantFix extended ephemeris technology for GPS and GLONASS is also supported.
The SiRFstarV 5t supports all four major GNSS. With its 24 additional satellites, GLONASS provides a valuable augmentation to GPS and enables the SiRFstarV 5t to boost location performance, especially in urban canyons, for the most demanding applications by increasing service availability, reducing observation time and making solutions more precise. The SiRFstarV 5t additionally supports Galileo and Compass systems, when they become available, with a software upgrade for even greater performance and ensured compliance to existing and future requirements of the world’s major GNSS systems.
The SiRFstarV 5t introduces CSR’s exclusive TricklePowerII technology, an improved intelligent power management system that can deliver significant power savings compared to other location solutions for continuous 1-Hz navigation. TricklePowerII continually measures the strength of the available satellite signals and dynamically adjusts the chip’s power consumption to just the right amount to achieve optimal location performance without wasting power. With many new mobile devices including MEMS (micro-electro-mechanical systems) sensors, the SiRFstarV 5t is able to utilize data from these sensors to improve navigation accuracy and reduce power.
The SiRFstarV 5t has been designed from the ground up to provide superior immunity to interference from LTE (long-term evolution) radio signals, giving mobile device manufacturers confidence in its ability to coexist in their designs with LTE, CSR said. Coexistence of LTE with GPS, GLONASS, and other GNSS signals is critical for continuous location awareness and use of location-based services, and CSR has implemented a number of mechanisms to boost immunity to LTE interference in the SiRFstarV 5t.
The SiRFstarV 5t also includes improved active jammer removal, a unique CSR technology first introduced with the SiRFstarIV architecture, which improves location performance by continually tracking and eliminating radio interference from up to eight sources, a critical requirement when GNSS devices are in close proximity to other electrically noisy devices like those found in a mobile handset.
The complete CSR solution includes SiRFNav software running on the host CPU to calculate the precise position, velocity and time and provide complete control of GNSS operation, including navigation, assistance and nav-aiding. The solution requires minimal OS-dependent host system loading during tracking, simplifying system integration, and supports a wide variety of CPUs and operating systems.
Galileo Flight Model #3 (FM3) is readied for the satellite’s fit check on the dispenser that will carry it and FM4 in a parallel arrangement on Soyuz’ next launch. The silver-colored dispenser is partly visible behind two mission team members during this activity in the Spaceport’s S1B payload preparation building.
Both Galileo navigation satellites for Arianespace’s third Soyuz flight from the Spaceport are now in French Guiana, marking a new milestone for this mission scheduled in the second half of 2012, according to Arianespace.
The Flight Model #4 (FM4) satellite arrived Friday at Félix Eboué International Airport near the capital city of Cayenne, delivered by a chartered Ilyushin Il-76TD cargo jetliner.
Its FM3 co-passenger remains busy in the Spaceport’s S1B payload preparation building — completing its fit check with the dispenser for the dual-satellite payload arrangement on Soyuz. The dispenser was developed for Arianespace by RUAG Space, and carries the satellites in a parallel arrangement.
These two spacecraft will join another pair of Galileo satellites launched by Arianespace in October 2011 on Soyuz’ maiden flight from French Guiana. All four are In-Orbit Validation platforms that will enable European industry to validate prototype Galileo-based receivers and services using actual satellite signals, while also allowing performance assessments of the ground system that will maintain the Galileo system’s precision.
Arianespace is responsible for deploying the entire Galileo constellation, to be composed of 30 satellites in orbit as an independent global satellite navigation system for Europe.
Galileo launches began with the 2005 and 2008 orbiting of two experimental satellites — GIOVE-A and GIOVE-B — carried on Soyuz vehicles operated from Baikonur Cosmodrome in Kazakhstan by Arianespace’s Starsem affiliate. It was followed by October 2011’s maiden Soyuz launch from French Guiana with the constellation’s first two operational satellites.
Arianespace is able to use a mix of both its medium-lift Soyuz and heavy-lift Ariane 5 launchers in deploying the full Galileo system, demonstrating the company’s flexibility in orbiting satellite constellations.
The photo shows FM4’s unloading from the Ilyushin Il-76TD cargo jetliner at Cayenne’s Félix Eboué International Airport.
The fourth Galileo flight model satellite being unloaded at Cayenne Airport in French Guiana on August 17. (Credits: ESA/EADS Astrium – Raoul Kieffer)
Spaceflight Now is reporting that the next GPS satellite, Block IIF-3 (SVN65) to be launched on October 4, 2012, will be positioned in orbital slot 1, which is in plane A. This slot is currently occupied by a Block IIA satellite, SVN39, operating as PRN09. SVN39 is one of the oldest operating satellites in the GPS fleet, having been launched on June 26, 1993.
This will be the third satellite in the Block IIF series of GPS spacecraft with improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation (and others) and a longer design life. Boeing is building a dozen craft to upgrade the constellation’s foundation over the coming years.
After more than four years of service as a Galileo test-bed satellite, GIOVE-B was retired on July 23. Its navigation transmitters were switched off and, according to an announcement from the European Space Agency, the satellite’s height was subsequently raised in a series of steps to place it in a so-called “graveyard” orbit where there will be no danger of it interfering with the operational Galileo satellites or other spacecraft.
After the first delta-V orbit manoeuvre, NORAD/JSpOC lost the satellite — at least NORAD/JSpOC stopped providing updated two-line orbital element sets for it. Eventually, 24 days later, the agency found it and resumed issuing element sets.
Just before the orbit manoeuvres, GIOVE-B had a mean motion of 1.70959839 orbits per day according to NORAD/JSpOC, which translates to an orbit semi-major axis value of approximately 29,544 kilometres. When NORAD/JSpOC recovered the satellite, its mean motion was 1.65377594 orbits per day with a semi-major axis of 30,205 kilometres, a change of 661 kilometres.
GPS World Survey and GIS editor Eric Gaskstatter attended the CGSIC (Civil GPS Service Interface Committee) State and Local Government subcommittee meeting in Seattle August 14, and provided a report in his Survey Scene editorial.
The Civil GPS Service Interface Committee (CGSIC) was established to facilitate communication among civilian GPS users, identify civilian user community needs, and report to the Office of the Assistant Secretary for Transportation. The U.S. state and local government subcommittee meeting moves around to different parts of the U.S. The next meeting is the annual CGSIC meeting, typically held the two days prior to the Institute of Navigation (ION) GNSS conference. This year it’s being held in Nashville, Tennessee.
Gakstatter reports on how GNSS receiver technology is moving much faster than GPS policymakers can keep up with, the National Telcommunications and Information Administration’s efforts to execute the National Broadband Plan, and a whether illegal jamming has been on the rise.
Tallysman Wireless, Inc., has announced the latest addition of the TW4320/4322 to its line of antenna products. The TW4320/TW4322 antennas are small wide-band, high-performance antennas housed in a compact IP67 magnetic mount enclosure, with a three-meter cable and a wide range of connectors.
“Most small low-cost GPS and GLONASS antenna have narrow-band patch elements tuned mid-way, but which are 2-dB down in both signal bands,” said Gyles Panther, CEO of Tallysman Wireless. “The TW4320/22 antennas feature a patch element with a 40% wider bandwidth and a very low noise amplifier which together allows the full benefits of multi-constellational GNSS to be realized.”
The TW4320/TW4322 antenna covers the GPS L1, GLONASS L1, and SBAS (WAAS, EGNOS, and MSAS) frequency bands (1575 to 1606 MHz). It features a small patch element with 40 percent wider bandwidth than previously available in this format. It provides both GPS-L1 and GLONASS signals in the 1-dB received power bandwidth.
The TW4320/TW4322 has a two stage low-noise amplifier with a mid-section SAW (Surface Acoustic Wave). A tight pre-filter is available in the TW4322 to protect against saturation by high-level sub-harmonics and L-band signals.
Features:
• 40% wider bandwidth in the same format
• Axial ratio: 6 dB max
• Low noise LNA: 1 dB
• High rejection mid-section SAW filter
• Available pre-filter (TW4322)
• High gain: 28 dB typ.
• Wide voltage input range: 2.5 to 10 VDC
• IP67 weather-proof housing
Models:
• TW4320 – GPS/GLONASS antenna, three-meter cable, SMA Male 32-4320-xx-yyyy
• TW4322 – GPS/GLONASS antenna, with pre-filter, three-meter cable, SMA Male 32-4322-xx-yyyy
The GPS Block IIR-M satellite, SVN49, resumed transmissions as PRN24 at about 18:35 UTC on August 9, 2012. The signals are marked unhealthy and the satellite is not included in broadcast almanacs. SVN49 was launched on March 24, 2009, but remains out of service until an L1/L2 satellite multipath issue is resolved.
China will build a testing and certification network for its Beidou satellite navigation system over the next three years to sharpen the system’s global competitiveness, according to a Friday statement from the Certification and Accreditation Administration, as reported by the Xinhua news service.
An authoritative testing and certification system with uniform standards and legal support will secure the Beidou system’s safe operation and accelerate its industrialization, said the statement. By 2015, a national testing center will be set up in Beijing, while another seven local sub-centers will be established across the nation, it said. The centers will test the safety and accuracy of products designed for use with the system and qualify them for civilian use.
China began to construct the Beidou system in 2000 with a goal of breaking its dependence on GPS by 2020. Authorities plan to launch a total of 30 satellites to complete the system. The 12th and 13th satellites will be launched at the end of April.
The Beidou system has been used by 120,000 civilian and military users to date, according to the statement.
India’s GSAT-10 telecommunications satellite — one of two passengers for Arianespace’s upcoming Ariane 5 mission in September — has been put through its paces during pre-flight preparations at the Spaceport in French Guiana, including a solar panel deployment test, according to Arianespace.
Also aboard GSAT-10 is the GAGAN (GPS and GEO augmented navigation) payload, which will support the Indian government’s implementation of a satellite-based regional capability to assist aircraft navigation over Indian airspace and in adjoining areas. The initial GAGAN payload was carried aboard the GSAT-8 spacecraft, orbited by Arianespace on an Ariane 5 mission in May 2011.
The solar panel checkout involved the extension of its multi-segment solar panels, validating the proper operation before they are definitively stowed against the satellite in the final lift-off configuration. The test uses an overhead latticework that helps support the solar panel’s weight — simulating zero gravity conditions of space as the panel opens to its full length.
Performed under the control of GSAT-10 satellite team members, the extension validation was conducted in the S5C high bay area of the Spaceport’s S5 payload preparation center — the largest individual hall in this facility.
GSAT-10 was developed by the Indian Space Research Organisation (ISRO), and will meet the growing need for Ku- and C-band transponder capacity. It is to become part of the Indian National Satellite (INSAT) system of geostationary spacecraft — representing one of the largest domestic communications satellite networks in the Asia-Pacific region.
Configured with 12 Ku-band, 12 C-band and 12 extended C-band transponders, GSAT-10 utilizes the I-3K satellite bus developed by ISRO, with a power capability of some six kilowatts and a liftoff mass estimated at 3,400 kg.
The upcoming Ariane 5 flight with GSAT-10 and the Astra 2F satellite as its co-passenger is set for September 21 from the Spaceport’s ELA-3 launch
complex. This will be Arianespace’s fifth mission from French Guiana in 2012 with the heavy-lift workhorse.
Below, one of GSAT-10’s two solar panels is extended during deployment verifications performed in the Spaceport’s S5 payload preparation center.
Tallysman Wireless, Inc., has announced the latest addition of the TW4320/4322 to its line of antenna products. The TW4320/TW4322 antennas are small wide-band, high-performance antennas housed in a compact IP67 magnetic mount enclosure, with a three-meter cable and a wide range of connectors.
