The China Academy of Launch Vehicle Technology announced the successful launch of the first geosynchronous satellite in China’s Compass constellation on July 31, 2010. China has already launched four geostationary satellites that will provide navigation coverage within the Asia-Pacific region by late 2012. The first geosynchronous satellite is part of China’s proposed plan to provide full global coverage by 2020, similar to what is currently provided by the United States’ GPS constellation.
Japan is also moving ahead with its Quasi-Zenith Satellite System (QZSS). The QZSS will provide navigation coverage for Japan and portions of the surrounding Asia-Pacific region, with full operational status anticipated in 2013. The first satellite was originally scheduled to launch on August 2, 2010, but the launch was postponed due to a suspected defect in the satellite’s reaction-wheel assembly system. The defective part has since been replaced, and the launch has been rescheduled for September 11, 2010.
The QZSS will provide high accuracy positioning to most of Japan, even where urban canyons or mountainous terrain might otherwise be an issue. Following a campaign by the Japanese Aerospace Exploration Agency (JAXA), the satellite has been nicknamed “Michibiki,” which means “guiding star” or “showing the way.” The satellite also has its own mascot as well as a dedicated website that will provide 3-D interaction and information about the satellite beginning on August 23.
The Quasi-Zenith Satellite System Orbit will keep a navigational satellite almost directly overhead at all times, providing greater positioning accuracy for GNSS users in Japan (public domain image courtesy of Wikimedia Commons).
The fourth navigation satellite in China’s Beidou or Compass constellation was successfully launched on June 2, 2010. This satellite is one of five planned geostationary satellites that will ultimately provide navigation coverage within the Asia-Pacific region. An additional thirty non-geostationary satellites are expected to be in place by 2020 in order to bring the Compass constellation to full global coverage similar to what is currently provided by the GPS constellation. China is planning to have a total of twelve satellites in orbit by the end of 2012 to provide positioning, timing and short messaging communication services for much of Asia and the Pacific region. The system is expected to provide a positioning accuracy of approximately thirty feet for civilian users. A more accurate service will be available to authorized and military users only.
Once all currently planned satellites have been deployed and added to those already in orbit in existing constellations, it is anticipated that positioning services, particularly in “urban canyons” and other locations where signal strength has previously been an issue, will be significantly enhanced for navigation system users around the world.
The Compass Navigation Satellite System will initially provide service to the Asia-Pacific region (public domain image courtesy of Wikimedia Commons).
After a week of delays caused by everything from technical malfunctions to bad weather, the first in a series of
GPS IIF satellites was
finally launched from Cape Canaveral late in the evening on May 27, 2010. A total of twelve IIF satellites are expected to launch through 2014, with the next launch tentatively scheduled for November 2010.
The IIF satellites are part of the ongoing modernization of the GPS constellation by the United States Air Force. The IIFs have improved atomic clocks used for timing and are therefore expected to provide more accurate navigation signals than those currently available from the rest of the GPS constellation. The IIFs will also broadcast the civil L5 signal for safety-of-life applications, which has the potential to enhance indoor reception with its wider bandwidth and lower frequency. The new satellites will also be compatible with the Galileo, GLONASS and QZSS constellations. In addition, the IIFs will assist the IIRM series already in orbit with military-specific M-code, a unique encryption for military users requiring secure access.
The new satellite, officially known as GPS IIF-1 SV-1, is expected to begin broadcasting its signal to GPS users following a three- to four-month testing period. In addition to being the first in the new IIF satellite series, this launch was significant for another reason as well. GPS IIF 1 SV-1 was carried into orbit on a Delta IV rocket, making it the first GPS satellite since 1985 that was not placed in orbit by an Atlas rocket.
The new IIF satellite series has finally launched. (Public domain image courtesy of http://pnt.gov/public/images/.)
Russia launched three additional GLONASS satellites on March 1, 2010. The launch was originally scheduled for September 2009, but had to be postponed when problems emerged with a similar satellite already in orbit and sent the three new satellites back to the factory for pre-launch repairs. The GLONASS constellation now includes 23 operational satellites, two of which are being used in a reserve capacity. A 21-satellite constellation provides 98.5% global availability. With three additional satellites expected to launch in August and another launch scheduled for November, the GLONASS constellation could reach 99.5% global availability by the end of 2010.
As a comparison, the current GPS constellation maintained by the United States includes 32 satellites and reached full operational capacity in 1995. It takes a minimum of 24 operational satellites to provide complete global availability.
A solar flare that occurred on February 12, 2010 may signal a return to high solar activity after several months of sustained low activity. Intense solar flares can cause temporary disruptions in GPS signals due to the high levels of radiation they release into the Earth’s atmosphere.
Solar activity generally occurs in eleven-year cycles, with the next peak expected by 2012. Increased solar activity is particularly troublesome for the navigation devices many drivers reference in their vehicles. GPS blackouts may last for a number of minutes during periods of peak solar activity and may occur several times each year. In addition to GPS blackouts, the atmospheric charge can impact the amount of time it takes for a GPS signal to make it to a GPS receiver, which causes inaccurate readings. Positioning may be off by as much as thirty feet during these periods, which will have the greatest impact on GPS survey equipment.
For iPhone users that want to keep track of solar activity, NASA has helped implement a new app called “3D Sun” that allows users to access a live global view of the sun. Data is provided in near real-time fashion by NASA’s STEREO mission, a pair of satellites that provide coverage of both sides of the sun simultaneously. More information on the app is available at http://3dsun.org/.
A high resolution 2D image of the sun taken by NASA's STEREO mission. STEREO is monitoring solar activity that may interfere with GPS and other signals. (Public domain image courtesy of NASA.)
China launched the third satellite in its Compass Navigation Satellite System on January 17, 2010. This satellite is one of five planned geostationary satellites that will ultimately provide navigation coverage within the Asia-Pacific region. An additional 30 non-geostationary satellites are expected to be in place by 2020 in order to bring the Compass constellation to full global coverage.
Also known as the Beidou system, the geostationary satellites will provide free open service within the local service area. A second level of service will provide greater accuracy to authorized users only.
GPS geometry dictates that a minimum of 24 satellites is necessary to provide complete global coverage. Properly configured within the GPS constellation, more satellites would mean improved coverage and ostensibly greater accuracy. Although the United States currently has 30 satellites in orbit, several of these are riding shotgun with older satellites and serving strictly in an auxiliary capacity, so the working constellation has remained steady at 24. However, things are about to change dramatically.
On January 11, 2010, following extensive feasibility studies, the U.S. Strategic Command (USSTRATCOM) announced that three of the augmentation satellites would be moved to new locations within the GPS constellation, thus effectively increasing the number of individually positioned satellites from 24 to 27. The main thrust of the reconfiguration is to increase coverage in previously degraded areas, such as the mountainous regions of Afghanistan, for military purposes. However, the changes will benefit civilian and commercial users as well.
The new “Expandable 24” configuration will take approximately two years to implement fully, but the first satellite is already on the move. Space Vehicle Number (SVN) 24 began its journey on January 13 and should arrive in its new position sometime in January 2011. The other two satellites have shorter journeys ahead of them. SVN 49 will begin its journey on January 21 and is expected to be in its new position by May 2010. SVN 26 will being its journey on February 8 and should also be in its new position sometime in May 2010.
From the mountainous regions of Afghanistan to the urban canyons of the United States, GPS users should begin to notice gradual improvements in GPS coverage over the next two years as the number of satellites visible from any location on earth begins to increase. I find it especially intriguing that two of the three satellites being moved are expected to be in place in May 2010, exactly 10 years after Selective Availability (SA) officially ended and GPS first became readily available to non-military users.
SVN 24, a GPS IIA satellite similar to the one in this image, is currently on the move to provide enhanced GPS coverage to users worldwide. The satellite is expected to arrive in its new location within the GPS constellation sometime in January 2011. (Public domain image courtesy of http://pnt.gov/public/images/.)
