Tag: GPS constellation

New GPS IIF Satellite Launched
A United Launch Alliance Delta IV lifts off from Space Launch Complex-37 with the Air Force’s Global Positioning System (GPS) IIF-5 satellite. This launch marked the 25th Delta IV flight since the first flight in 2002. Credit: Ben Cooper/ULA

News compiled with the assistance of CANSPACE listserv.

After a brief delay due to concerns over solar radiation trends, the GPS IIF-5 satellite was successfully launched at the end of the designated launch window at 01:59 UTC on February 21. The satellite, attached to the launch rocket’s upper stage, was initially placed in a highly elliptical orbit. Following a third burn of the rocket, the satellite was released into its assigned orbit at about 05:37 UTC today.

Here is a video showing highlights of the launch:

GPS IIF-5 will replace the aging spacecraft known as GPS IIA-28 in Plane A, Slot 3 of the constellation.The GPS IIA-28 satellite was launched aboard Delta 249 on November 5, 1997, as the final member of the Block IIA series. It will go into a reserve role in the network for the remainder of its useful life.

This is the first of three GPS launches planned through July to replace aging craft in the constellation. GPS IIF-5 incrementally upgrades the constellation with improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation, and a longer design life, all features of the Boeing-build Block IIF series. This will be the fifth of 12 Block IIF spacecraft being built to form the backbone of the GPS fleet for the next 15 years.

Launch logo. The nickname of the IIF-5 satellite is Canopus, the brightest star in the modern constellation Carina and the second brightest star in the night-time sky, after Sirius.

According to the Air Force, the new capabilities of the IIF satellites will provide greater navigational accuracy through improvements in atomic clock technology, a more robust signal for commercial aviation and safety-of-life applications, known as the new third civil signal (L5), a second civil signal (L2C) available for the dual-frequency GPS receivers and a 12-year design life providing long-term service. These upgrades improve anti-jam capabilities for the warfighter and improve security for military and civil users around the world.

“I am pleased with the outcome of today’s launch. The new capabilities provided by the IIF satellites will improve operations, sustainment and overall GPS service for the warfighter, international, commercial and civil communities,” said Col. Bill Cooley, director of the Space and Missile Systems Center’s Global Positioning Systems Directorate.

“The modernized capabilities that are coming on board with the successful launch of GPS IIF-5 will support the worldwide GPS community for years to come. I would like to recognize the outstanding commitment and the superb dedication to mission success from the 45th and 50th Space Wings, our industry partners: Boeing and United Launch Alliance, and the GPS IIF and Delta IV program teams at the Space and Missile Systems Center,” said he said.

The GPS Block IIF satellites are built by Boeing, and are operated by the United States Air Force following their launch by United Launch Alliance, using Evolved Expendable Launch Vehicles.
- The first GPS IIF satellite was launched on May 27, 2010, and entered service on Aug. 26, 2010.
- The second satellite, which launched on July 16, 2011, entered service on Aug. 22, 2011.
- The third satellite launched on Oct. 4, 2012, and entered service 22 days later.
- The fourth IIF was launched May 15, 2013, and entered service on June 21, 2013.
Every modern GPS satellite was launched from Cape Canaveral Air Force Station.

Each GPS IIF satellite delivers:
- Greater navigational accuracy through improvements in atomic clock technology,
- A new civilian L5 signal to aid commercial aviation and search and rescue operations,
- Improved military signal and variable power for better resistance to jamming in hostile environments,
- A 12-year design life providing long-term service and reduced operating costs,
- An on-orbit, reprogrammable processor that can receive software uploads for improved system operation.
“Once again, a group of talented mission partners rose to the challenge of launching another successful mission from the Cape,” said Col. Douglas Schiess, commander, 45th Operations Group, who served as the Launch Decision Authority. “Those mission partners include the 45th Space Wing, the Space and Missile Systems Center, the 50th Space Wing, United Launch Alliance, Boeing, and our other industry partners with the Delta IV and GPS IIF launch teams.”

A United Launch Alliance Delta IV lifts off from Space Launch Complex-37 with the Air Force’s Global Positioning System (GPS) IIF-5 satellite. This launch marked the 25th Delta IV flight since the first flight in 2002.

A United Launch Alliance Delta IV lifts off from Space Launch Complex-37 with the Air Force’s Global Positioning System (GPS) IIF-5 satellite. This launch marked the 25th Delta IV flight since the first flight in 2002.
February 21, 2014
GPS Satellite Launch Set for Thursday

The United Launch Alliance Delta 4 rocket family will launch a new GPS IIF satellite from Cape Canaveral Thursday night.

Liftoff is scheduled for Thursday at 8:40 p.m. EST, at the start of a 19-minute launch opportunity, according to the United Launch Alliance. The window is timed to deliver the GPS IIF-5 satellite directly into Plane A of the navigation network 11,000 miles above Earth.

GPS IIF-5 will replace the aging spacecraft known as GPS IIA-28 in Plane A, Slot 3 of the constellation. The GPS IIA-28 satellite was launched aboard Delta 249 on November 5, 1997, as the final member of the Block IIA series. It will go into a reserve role in the network for the remainder of its useful life.

Spaceflight Now will host a live stream of the launch.

This is the first of three GPS launches planned through July to replace aging craft in the constellation. GPS IIF-5 incrementally upgrades the constellation with improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation, and a longer design life, all features of the Boeing-build Block IIF series. This will be the fifth of 12 Block IIF spacecraft being built to form the backbone of the GPS fleet for the next 15 years.

The Delta’s flight will last three hours and 33 minutes from liftoff until spacecraft separation, firing its cryogenic upper stage in three different burns to reach an initial parking orbit and taking a two-step transfer route to reach the circular GPS orbit tilted 55 degrees to the equator.

February 18, 2014
Who Carries the Gold Standard Now?

China’s BeiDou system claimed a user range error (URE) of 2.5 meters zero age of data (ZAOD) 95% recently. The parallel GPS specifications commit to 6 meters 95% ZAOD and 7.8 meters 95% all AODs. Does this mean that BeiDou is more accurate than GPS? Not so fast.

In late December, director Ran Chengqi of China’s Satellite Navigation System Management Office announced the BeiDou Navigation Satellite System (BDS) Public (or Open) Service Performance Standard. The document details the public service performance parameters of the BeiDou system, including service area, accuracy, integrity, continuity, and availability. It is a basic commitment to customers from BDS providers, but also an important basis for customers to choose, use, and evaluate the system performance.

A few important qualifications of BeiDou’s performance standard first:

According to the foreword of the document, “This document specifies the BDS open service performance standard at the current stage.” This is as it should be.

A paragraph on service volume, however, highlights the fact that BeiDou is as yet a regional service.

“4.4 BDS OS Service Volume

The BDS OS service volume is defined as the OS SIS coverage of the BDS satellites where both the BDS OS horizontal and vertical position accuracy are better than 10 meters (probability of 95%). At the current stage, the BDS regional service capability has been achieved, which can provide continuous OS to the area as shown in Figure 2 & Figure 3, including the most part of the region from 55°S to 55°N, 70°E to150°E.”

The BDS Service Area.

This means that BeiDou commits to 2.5 meter accuracy in China, as well as neighboring countries — and importantly, trading partners — in Southeast Asia plus Australia.

Does this mean that once BeiDou attains global status, it will provide 2.5 meter accuracy everywhere, on its basic single frequency, open service? Hard to tell. Much of its strength, its core strength, one might say, comes from 5 geostationary Earth orbit (GEO) satellites and 5 Inclined Geosynchronous Satellite Orbit (IGSO) satellites. The GEOs hover over the Equator more or less permanently, south of but in the general longitude of China’s sovereign national territory. The IGSOs move back and forth from the northern to the southern hemispheres in the same area.

When BeiDou achieves its planned global reach, an event scheduled for 2020, the constellation will consist of 35 satellites: 5 GEOs, stationed at longitudes so their footprints cover China, 27 medium Earth orbit (MEO) satellites encircling the globe in continuous paths as do those of GPS, and 3 IGSOs over the East and Southeast Asian regions.

Will globally available accuracy at that point match what is achievable in China? It takes a better geometric mind than mine to fathom this.

Even disregarding the geographic limit of the 2.5-meter claim, and ignoring for the moment the mathematical conundrum outlined above, there are reasons to scrutinize the BeiDou Performance Standard more closely, as John Lavrakas of Advanced Research Corporation has done. His notes, and an illuminating table, follow below after a bit more introduction and background on the general topic.

The publishing of the Public Service Performance Standard, a common practice among GNSS operators, is also a prerequisite for BeiDou system involvement in international civil aviation, international maritime, 3rd Generation Mobile [phone] System, and other international standard-setting organization activities.

The document has Chinese and English versions. Because document download from the BDS government website can be difficult, Richard Langley has made them available at the University of New Brunswick website:

http://www2.unb.ca/gge/Resources/beidou_open_service_performance_standard_ver1.0.pdf

http://www2.unb.ca/gge/Resources/beidou_icd_english_ver2.0.pdf

Analysis

John Lavrakas of Advanced Research Corporation posted the following comment to the an earlier online article announcing the Performance Standard document.

“I took a quick look at comparing the BeiDou Open Service Performance Standard with the GPS Standard Positioning Service Performance Standard and obtained mixed results.”

Table 1. Coded to show green for the GNSS service committing to a more stringent standard over the other. Courtesy of Advanced Research Corporation.

“In some cases, the commitments from BeiDou were stronger (URE accuracy, vertical position), and in other cases the commitments from GPS were stronger (continuity of service, advance notice of outages).

“The good news is that GNSS systems are documenting the service levels that users can expect. What we will need next is monitoring to verify these service levels are being met.

“Here is a link to my quick look:

http://oregonarc.com/2014/01/beidou-performance-standard-how-good-is-it/.”

Thank you, John.

A final note. As the GPS stewards from the U.S. Air Force carefully and proudly remind us at each GNSS conference where they deliver a briefing, actual GPS performance has almost always bettered its specs over the last decade or two — often by a considerable margin.

And with that, I think we may all return to our various pursuits, secure in the knowledge that while the gold standard may — repeat, may — at times pass in limited special circumstances or under particular conditions, from system to system, overall GNSS Things Are Getting Better All the Time.

January 28, 2014
Extra Life for IIRs, IIR-Ms

U.S. Air Force engineers are testing on-orbit a technique to extend the life of the 19 GPS IIR and IIR-M satellites on orbit, roughly 60 percent of the current constellation.

A new charging method may reduce the rate of satellite battery degradation, thereby extending satellite operational life. If the technique passes the test, the initiative could add a combined 20 years to the life of the satellites — saving the Air Force tens of millions of dollars in the process.

Gen. William Shelton, commander of Air Force Space Command, credits Capt. Jacob Hempen of the Air Force’s 2nd Space Operations Squadron for the job. Capt. Hempen says in turn that Warren Hwang of the Aerospace Corporation originated the idea.

When satellite solar panels are directly exposed to the Sun, they charge satellite batteries while continuing to power other operations on board the space vehicle. When the satellite passes into the Sun’s shadow behind the Earth, it runs on batteries. The batteries can be recharged at variable rates. When some of the batteries are powered above a certain rate threshold, they can overheat, accelerating their natural rate of decay.

Lowering battery charging rates could still enable the satellites to perform well while minimizing the rate of degradation. Hitting the optimum number called for some finely-honed calculations.

The satellites were built by Lockheed Martin Space Systems, and the oldest still in operation was launched in 1997. They had an initial design life of eight years, which many have now well outlasted. If the technique proves out and is carefully applied across the board, it could conceivably fill in replenishment gaps equivalent more than two additional spacecraft — conceivably as much hundreds of millions of dollars in build and launch costs, postponed. In today’s budget environment, a postponement can be construed as equivalent to outright savings.

August 29, 2013

2C or Not 2C: The First Live Broadcast of GPS CNAV Messages

By Oliver Montenbruck, Richard B. Langley, and Peter Steigenberger

Over the past several years, some users of the GPS navigation system have already benefitted from the addition of various new signals in addition to the legacy C/A- and P(Y)-code. With the introduction of the Block IIR-M satellites in 2005, a new civil signal (L2C) was transmitted on the L2 frequency, and a new signal on a new frequency (L5) was introduced as a standard signal with the Block IIF satellites beginning in 2010. These new signals provide direct access to dual-frequency observations and thus enable improved ionospheric corrections for civil, including aeronautical, users. In addition, a new Civil Navigation (CNAV) broadcast message has been defined in the GPS Interface Specifications (IS-GPS-200 and IS-GPS-705).

This message will be transmitted jointly on the L2C and L5 signals and provides a variety of useful new parameters. Compared to the legacy L1 C/A-code navigation message, the CNAV message also offers an increased flexibility concerning the type, sequence, and repeat rate of specific messages.

CNAV messages have already been broadcast over the past two years by the Michibiki (QZS-1) satellite of the Japanese Quasi-Zenith Satellite System (QZSS), which shares many aspects of the GPS signal design. In contrast to this, Block IIR-M and IIF GPS satellites have only transmitted dummy messages so far and a fully operational CNAV transmission is only foreseen once the ongoing modernization of the GPS control segment has been completed.

Triggered by various interest groups, the Global Positioning Systems Directorate has just conducted a first test campaign with live CNAV transmissions on L2C and L5 over the two-week period from June 15 to 29 (see Global Positioning System Modernized Civil Navigation (CNAV) Live-Sky Broadcast Test Plan.) It served as a first opportunity for end users and receiver manufacturers to test the decoding and use of the new messages under a wide range of different configurations.

CNAV messages have a common length of 300 data bits and are identified by a message type number that signifies their contents. The messages presently defined for GPS are summarized in Table 1. For QZSS, complementary messages have been established, which enable, among other features, a rebroadcast of GPS-specific data to QZSS users.

Table 1. Summary of CNAV message types transmitted by space vehicles (SVs). Messages marked by an asterisk were transmitted during the recent CNAV test campaign.

Message Type	CNAV Message Title	Function/Purpose
0*	Default	Default message (transmitted when no message data is available)
10*	Ephemeris 1	SV position parameters for the transmitting SV
11*	Ephemeris 2	SV position parameters for the transmitting SV
12*	Reduced Almanac	Reduced almanac data packets for seven SVs
13	Clock Differential Correction	SV clock differential correction parameters
14	Ephemeris Differential Correction	SV ephemeris differential correction parameters
15*	Text	Text (29 eight-bit ASCII characters)
30*	Clock, Iono & Group Delay	SV clock correction parameters, ionospheric and group delay correction parameters (inter-signal correction parameters)
31	Clock & Reduced Almanac	SV clock correction parameters, reduced almanac data packets for four SVs
32*	Clock & EOP	SV clock correction parameters, Earth orientation parameters; Earth-centered, Earth-fixed to Earth-centered inertial coordinate transformation
33*	Clock & UTC	SV clock correction parameters, Coordinated Universal Time parameters
34	Clock & Differential Correction	SV clock correction parameters, SV clock and ephemeris differential correction parameters
35*	Clock & GGTO	SV clock correction parameters, GPS to GNSS time-offset parameters
36	Clock & Text	SV clock correction parameters, text (18 eight-bit ASCII characters)
37	Clock & Midi Almanac	SV clock correction parameters, midi (mid-accuracy) almanac parameters

Other than the legacy L1 navigation message, which adheres to a fixed order of subframes, the sequence of CNAV messages can be varied widely to provide users with an optimized set of low latency information and parameters that change infrequently. As a baseline, the two ephemeris message types 10 and 11 are combined with any of the clock-and-auxiliary data messages (types 30 through 37) to provide users with the orbit and clock data of the received satellites. With a transmission duration of 12 seconds per CNAV message on L2C, a minimum of 36 seconds is required to transfer this information to the user if no other messages are transmitted. On L5, which operates at twice the data rate, a new frame is transmitted once every 6 seconds yielding a minimum of 18 seconds for the broadcast of ephemeris and clock data.

The recent test campaign started at 18:00 GPS Time on Saturday, June 15, 2013, with the transmission of message types 10, 11, 15, and 30 on a first space vehicle (PRN24) and included PRN12 from 18:42 onwards. Other space vehicles were sequentially phased in until all active IIR-M and IIF satellites (except for the recently launched IIF-4 satellite) transmitted CNAV on the supported signals. When the test ended exactly two weeks later (June 29, 18:00 GPST), all participating satellites were transmitting a complex master frame of 15 x 4 = 60 individual messages, which was repeated once every 12 minutes (on L2C). Each minor frame comprised the two ephemeris messages and at least one clock-data message (see Table 2).

Table 2. Sequence of message types in a CNAV master frame.

Message Types
10	11	15	30
10	11	32	33
10	11	12	35
10	11	12	30
10	11	12	33
10	11	12	35
10	11	12	30
10	11	32	33
10	11	15	35
10	11	32	30
10	11	12	33
10	11	12	35
10	11	12	30
10	11	12	33
10	11	12	35

Other messages included a reduced almanac (message type 12) and a text message (message type 15) with dummy content (“THIS IS A GPS TEST MESSAGE.”)

The CNAV data were recorded by selected multi-GNSS monitoring stations of the German Aerospace Establishment (Deutsches Zentrum für Luft- und Raumfahrt or DLR) and the University of New Brunswick (UNB), which were specifically configured to record raw GPS navigation frames in addition to the normal observation data. The stations are located at Singapore (SIN0); Sydney, Australia (UNX2); Maui, U.S.A. (MAO0); and Hartebeesthoek, South Africa (HRAG); as well as Fredericton, Canada (UNB) and are equipped with either Javad Delta-G2/G3TH or NovAtel OEM6 receivers. Following initial validation, the raw and decoded data from the CNAV test will be made available to interested users through the Multi-GNSS Experiment (MGEX) of the International GNSS Service (see http:/igs.org/mgex) to facilitate the development of user software and suitable data formats (such as an extended RINEX navigation message format).

The CNAV orbit and clock data were updated once every two hours and offer a slightly higher bit resolution than their legacy counterparts. However, the accuracy of the ephemeris data has not yet been evaluated nor compared to that of the L1 C/A-code navigation data.

As indicated above, the CNAV data can also provide a particularly compact form of almanac data known as the reduced almanac. It does not offer clock information (that is not normally required for a signal search) and assumes a circular orbit, which reduces the overall accuracy. Still, it can be transmitted (and repeated) in a much shorter time interval than the legacy almanac, which requires a total of 12.5 minutes. Each reduced almanac message (message type 12) provides orbit information for a total of seven satellites and it takes a set of five such messages to convey information for a complete constellation. For the master frame layout described above, the full constellation reduced almanac is repeated twice within 12 minutes on L2C (and half this time on L5).

Novel types of CNAV data not covered by the legacy navigation message include the differential code biases (also known as inter-system corrections or ISCs), which are required for pseudorange-based positioning with signals other than the legacy P(Y)-code (in addition to the established Timing Group Delay parameter or TGD). An overview of TGD and ISC values broadcast by the various satellites participating in the CNAV test is given in Table 3.

Table 3. Differential code biases (in nanoseconds) of GPS Block IIR-M and IIF satellites broadcast during the test campaign as part of the message type 30 CNAV messages.

SV Type	SVN	PRN	TGO	ISC L1CA	ISC L2C	ISC L5I5	ISC L5Q5
IIR-M	48	07	-10.71	-0.84	6.52
IIR-M	50	05	-10.24	-0.32	5.41
IIR-M	52	31	-13.04	-0.55	7.36
IIR-M	53	17	-10.24	-0.84	6.17
IIR-M	55	15	-10.24	-0.47	5.62
IIR-M	57	29	-9.31	-0.76	5.06
IIR-M	58	12	-12.11	-0.76	6.64
IIF	62	25	5.59	-2.07	-5.24	-0.38	-0.87
IIF	63	01	8.38	-2.30	-7.57	0.38	2.15
IIF	65	24	2.79	-0.26	-2.27	2.27	3.70

Another important achievement is the provision of Earth orientation parameters (EOP) in message 32, which provides GPS users with access to the celestial reference frame. EOPs were transmitted during the second test week and updated on a daily basis (see Table 4). Knowledge of these parameters is of particular interest for GPS-based orbit determination and navigation of spacecraft (in low Earth orbit), which is preferably referred to an inertial rather than an Earth-fixed coordinate system.

Table 4. Daily Earth orientation parameters from the CNAV test campaign (pole coordinates and dUT1 (UT1-UTC) time differences and derivatives).

Epoch (GPST)	x_p (arcseconds)	x_p_dot (arcseconds per day)	y_p (arcseconds)	y_p_dot (arcseconds per day)	dUT1 (seconds)	dUT1_dot (seconds per day)
June 22, 0:00	0.13517	0.00104	0.39657	-0.00054	0.06341	-0.00046
June 23, 0:00	0.13621	0.00102	0.39604	-0.00056	0.06295	-0.00049
June 24, 0:00	0.13740	0.00101	0.39535	-0.00058	0.06231	-0.00053
June 25, 0:00	0.13815	0.00099	0.39487	-0.00060	0.06164	-0.00063
June 26, 0:00	0.13846	0.00096	0.39443	-0.00062	0.06078	-0.00067
June 27, 0:00	0.13885	0.00094	0.39381	-0.00064	0.06004	-0.00067
June 28, 0:00	0.13947	0.00093	0.39310	-0.00066	0.05909	-0.00063
June 29, 0:00	0.13987	0.00090	0.39246	-0.00068	0.05842	-0.00053

Overall, CNAV offers exciting prospects for improved GPS utilization and users may look forward to the next test campaigns, which will tentatively be conducted once every six months.

As a side note, it should be mentioned that individual satellites could be observed to transmit various types of non-standard CNAV messages as well as CNAV messages with improper data (such as an invalid week count) after the end of the main test campaign. Various receivers in the MGEX network, which were processing the received CNAV messages internally and which put full confidence in their proper contents, were mislead by such information. During the actual test campaign, all data appeared fully valid and no problems were reported by the stations.

OLIVER MONTENBRUCK is the head of the GNSS Technology and Navigation Group at DLR’s German Space Operations Center in Oberpfaffenhofen, Germany.

RICHARD B. LANGLEY is a professor in the Department of Geodesy and Geomatics Engineering at the University of New Brunswick, Fredericton, New Brunswick, Canada.

PETER STEIGENBERGER is a staff member in the Institut für Astronomische und Physikalische Geodäsie of the Technische Universität München (TUM) in Munich, Germany.

July 8, 2013

Update: GPS IIF-4 Successfully Launched from Cape Canaveral

UPDATE, May 24, by Richard Langley: The Centaur upper stage with the payload still attached was photographed from Tavistock, Devon, in the U.K. by Andy Smith. As can be seen from the ground trace figure in an earlier GPS World news item, the Centaur passed over the U.K. following MECO1, the first main engine cutoff. From Europe, the Centaur could be easily seen by reflected sunlight against the background stars. Its maximum (apparent) brightness magnitude has been estimated as -1 or -2. (Sirius, the brightest star in the night sky, has a magnitude of -1.5; Betelgeuse in the constellation Orion has a mean magnitude of about 0.4; and the limiting visual magnitude for the unaided eye is about 6.)

Smith’s photograph was taken at 21:58:38 UTC (start) with a Canon EOS 450D Digital Rebel camera with an 18-55mm zoom lens. The camera settings were: focal length 55mm, aperture f/5.6, and an exposure of 8 seconds at an ISO value of 1600. Two images are shown below: the original, as obtained from the camera, and a greyscale image with edge enhancement.

The Centaur can be seen traveling left to right and starts its track as it crosses the constellation of Cygnus. There’s a slight wobble at the beginning as the shutter release was pressed. The glow at the bottom of the frame is from a streetlight. The elevation angle of the Centaur was approximately 12 degrees.

SVN66 will operate as PRN27 and it will eventually occupy the C-2 orbital slot, replacing SVN33/PRN03, a Block IIA satellite launched in 1996. SVN66 is currently in a drift orbit about 400 kilometers above the operational constellation. It should reach the C-2 slot within a few days from now. The satellite has already been added to the broadcast almanac although it has not yet started to transmit standard signals. It is currently marked as unhealthy in the almanac and will remain so, even after standard signals are switched on, until testing is completed sometime this summer.

Centaur upper stage with the payload still attached, original photo. Photo credit: Andy Smith

The same photo digitally enhanced:

Digitally enhanced photo. Photo credit: Andy Smith

Photo credit: Pat Corkery, United Launch Alliance.

A U.S. Air Force Global Positioning System satellite built by Boeing was successfully launched May 15. The fourth GPS IIF satellite, Space Vehicle Number (SVN) 66, was carried aboard a United Launch Alliance Atlas V Launch Vehicle at 5:38 p.m. EDT (21:38 UTC) May 15 from Cape Canaveral Air Force Station, Florida.

The new capabilities of the IIF satellites will provide greater navigational accuracy through improvements in atomic clock technology; a more robust signal for commercial aviation and safety-of-life applications, known as the new third civil signal (L5); and a 12-year design life providing long-term service. These upgrades improved anti-jam capabilities for the warfighter and improved security for military and civil users around the world, the Air Force said in a statement.

The Atlas rocket took off on schedule. The satellite was released from the Centaur upper stage at T+ 3 hours, 23 minutes and 52.8 seconds or about 01:02 UTC on May 16. Details on the Block IIF satellites and the Atlas rocket can be found here.

“I’m extremely pleased with today’s launch and delighted to be part of this mission that enhances our nation’s critical GPS capability. Thanks to the superb efforts of the of the 45th and 50th Space Wings, United Launch Alliance, our industry partners, the Atlas V and GPS IIF launch teams, the GPS IIF-4 mission was successfully carried out,” said Col. Bernie Gruber, director of the Space and Missile Systems Center’s Global Positioning Systems Directorate.

“The GPS constellation remains healthy and continues to meet and exceed the performance standards to which the satellites were built. Our goal is to deliver sustained, reliable GPS capabilities to America’s warfighters, our allies and civil users around the world, and this is done by maintaining GPS performance, fielding new capabilities and developing more robust modernized capabilities for the future,” said Colonel Gruber.

Here are videos of the launch:

Opening photo by Pat Corkery, United Launch Alliance.

Photos show the launch of the U.S. Air Force’s GPS IIF-4 satellite from the Kennedy Space Center and Cape Canaveral Air Force Station.

Photo credit: Stephen Clark/Spaceflight Now

Photo credit: Stephen Clark/Spaceflight Now

Photo credit: Pat Corkery, United Launch Alliance.

Photo credit: Walter Scriptunas II/Spaceflight Now

Photo credit: Walter Scriptunas II/Spaceflight Now

Photo credit: Walter Scriptunas II/Spaceflight Now

Photo credit: Pat Corkery, United Launch Alliance.

Photo credit: Walter Scriptunas II/Spaceflight Now

May 24, 2013
Lockheed Martin Team Completes Delta Preliminary Design for Next GPS III Satellite Capabilities

Lockheed Martin has successfully completed a Delta Preliminary Design Review (dPDR) for the next Global Positioning System (GPS) III satellite vehicles planned under the U.S. Air Force’s GPS III program.

The GPS III program will replace aging GPS satellites, while improving capability to meet the evolving demands of military, commercial and civilian users. GPS III satellites will deliver three times better accuracy and up to eight times improved anti-jamming signal power while enhancing the spacecraft’s design life and adding a new civil signal designed to be interoperable with international GNSS.

The Air Force plans to purchase up to 32 GPS III satellites. Lockheed Martin is under contract for production of the first four GPS III satellites, and has received advanced procurement funding for long-lead components for the fifth, sixth, seventh and eighth satellites. The successful dPDR addresses design modifications, agreed on by the Air Force and the Lockheed Martin-lead industry team, which will provide new capabilities for GPS III Space Vehicle 9 (SV09) and beyond, including the addition of a search and rescue satellite payload and a Laser Retroreflector Array (LRA). An innovative new waveform generator permits the addition of new navigation signals after launch to upgrade the constellation without the need to launch new satellites.

“We have worked very closely with the Air Force and GPS community to make GPS III the most affordable and lowest risk solution for bringing new capabilities to the GPS constellation,” said John Frye, Lockheed Martin’s GPS III capability and affordability insertion manager. “The design modifications from this dPDR address ways to further reduce Air Force launch costs by $50 million per satellite through dual launch of two GPS III space vehicles on a single booster. This successful dPDR milestone sets the stage to proceed with SV09 design maturation.”

From the beginning of the program, the Lockheed Martin team has remained focused on affordability for GPS III, the company said, while working to ensure the enhanced satellite system can evolve to continue to meet the world’s global navigation and timing needs for the next 30 years. To help reduce risks and cut costs, the GPS III team developed a GPS Non-Flight Satellite Testbed (GNST), which serves as the program’s ground pathfinder and vehicle demonstrator for the first complete satellite. The entire GPS III development and production sequence uses the GNST to provide space vehicle design level validation; early verification of ground support and test equipment; and early confirmation and rehearsal of transportation operations.

Lockheed Martin team has met recent milestones and appears to be on track to deliver the first GPS III satellite, for launch availability in 2014.

In February, the Lockheed Martin team successfully turned on power to the system module of the program’s first spacecraft, designated GPS III Space Vehicle 1 (SV01), demonstrating mechanical integration, validating the satellite’s interfaces, and leading the way for electrical and integrated hardware-software testing. The satellite will complete its Assembly, Integration and Test (AI&T) in Lockheed Martin’s new GPS Processing Facility (GPF) designed for efficient and affordable satellite production.

The GPS III team is led by the Global Positioning Systems Directorate at the U.S. Air Force Space and Missile Systems Center. Lockheed Martin is the GPS III prime contractor with teammates ITT Exelis, General Dynamics, Infinity Systems Engineering, Honeywell, ATK and other subcontractors. Air Force Space Command’s 2nd Space Operations Squadron (2SOPS), based at Schriever Air Force Base, Colorado, manages and operates the GPS constellation for both civil and military users.

April 11, 2013
Upcoming GNSS Satellite Launches Scheduled

News courtesy of CANSPACE Listserv.

Satellites expected to be launched in support of various Global Navigation Satellite Systems are the following:

GPS
May 15: Block IIF-4, SVN66, launch window: 17:39-17:58 UTC
November: Block IIF-5

GLONASS
April 26: Single GLONASS-M or -K satellite from Plesetsk
June 28: Three GLONASS-M satellites from Baikonur

Galileo
October: FOC-1 launch (two satellites)

Indian Regional Navigation Satellite System (IRNSS)
June (This is the first launch for an expected constellation of seven satellites, some of which will be geostationary. The constellation will provide continuous regional coverage for positioning, navigation and timing services.)

March 18, 2013
SNV49 Off the Air?

News courtesy of CANSPACE Listserv.

It appears that GPS SVN49, the Block IIR-M satellite with the problematic L5 test transmitter and operating most recently as PRN27, stopped transmitting standard L-band signals on March 13. No International GNSS Service tracking station has observed the satellite since that date.

The satellite was being used for tests, was set unhealthy, and had not been included in broadcast almanacs.

March 16, 2013
Lockheed Martin Completes GPS III Flight Software Milestone

The Lockheed Martin team developing the U.S. Air Force’s next generation Global Position System III satellites has completed a key flight software milestone validating the software’s ability to provide reliable and effective command and control for the GPS III satellites planned for launch into orbit.

The GPS III program will affordably replace aging GPS satellites, while improving capability to meet the evolving demands of military, commercial and civilian users. GPS III satellites will deliver better accuracy and improved anti-jamming power while enhancing the spacecraft’s design life and adding a new civil signal designed to be interoperable with international global navigation satellite systems.

The milestone, known as Software Item Qualification Testing (SIQT), was completed for the satellite’s spacecraft bus flight software, which is critical to controlling the spacecraft on orbit and monitoring the health and safety of the satellite’s subsystems. SIQT included 131 individual test events and represented the culmination of a rigorous software engineering risk reduction and development phase. The software will next be integrated and tested on the first GPS III satellite, which is on schedule for launch availability in 2014.

“Completion of this flight software milestone demonstrates our continued positive program momentum and is another step forward in reducing risk up front to facilitate long term affordability,” said Lt. Col. William ‘Todd’ Caldwell, the U.S. Air Force’s GPS III program manager. “In this challenging budget environment, the entire government and industry team is focused on delivering the critical GPS III satellites affordably and efficiently for users worldwide.”

To further reduce risk, the flight software has already been integrated and tested on the program’s satellite prototype, known as the GPS III Non-Flight Satellite Testbed (GNST).

“Delivering fully qualified flight software this early in program development demonstrates the rigor of our GPS III software development processes,” said Keoki Jackson, vice president of Lockheed Martin’s Navigation Systems mission area. “Through up-front investments in high-fidelity, flight equivalent hardware and software testbeds, our team successfully executed on schedule to develop and qualify the flight software critical to the success of the GPS III program.”

Lockheed Martin is on contract to deliver the first four GPS III satellites for launch. The Air Force plans to purchase up to 32 GPS III satellites.

The GPS III team is led by the Global Positioning Systems Directorate at the U.S. Air Force Space and Missile Systems Center. Lockheed Martin is the GPS III prime contractor with teammates ITT Exelis, General Dynamics, Infinity Systems Engineering, Honeywell, ATK and other subcontractors. Air Force Space Command’s 2nd Space Operations Squadron (2SOPS), based at Schriever Air Force Base, Colorado, manages and operates the GPS constellation for both civil and military users.

February 6, 2013
Exelis Wins Air Force Contract to Research Low-Cost GPS Alternatives

ITT Exelis has been awarded a $2.15 million contract by the Air Force Research Laboratory (AFRL) to research the development of a small satellite navigation payload to augment the current GPS program. The GPS NAVSAT (Navigation Satellite) program seeks to provide affordable capabilities to aid end-users located in tough-to-reach environments.

“The development of smaller satellites — in terms of size, weight, power and cost — will yield greater affordability for our customers,” said Mark Pisani, vice president and general manager, Precision Instruments and Positioning, Navigation and Timing Systems, ITT Exelis Geospatial Systems. “A smaller satellite size will allow for improved launch vehicle selection flexibility.”

The goal of the 18-month initial study is to identify innovative ways to increase affordability and sustainment of the GPS program through payload weight reduction, size and power. The GPS NAVSAT will maintain similar performance capability to the existing GPS system, but will aid GPS end-users in signal-constrained environments, located in urban or mountainous terrain.

Work on GPS NAVSAT is performed in Clifton and Bloomfield, New Jersey.

For nearly 40 years, Exelis payloads and payload components have been on board every GPS satellite with more than 500 years of on-orbit life without a single mission-related failure due to Exelis equipment.

January 23, 2013
Launch of GPS Satellite Struggled through Tense Moments

A new report by Spaceflight Now reveals that the launch October 4 of a GPS satellite experienced tense touch-and-go moments.

The Delta 4 rocket’s cryogenic upper stage engine experienced a fuel leak that caused a low-thrust condition. Four-and-a-half minutes into the launch, after the first stage had shut down and separated, the trouble began as the RL10B-2 engine on the upper stage extended its nozzle and fired to life.

When the powerplant was igniting and reached its peak chamber pressure, a leak started above the narrow throat portion of the thrust chamber, setting off a chain of nail-biting events over the next three hours as the vehicle made its climb to the GPS constellation. The Delta 4 made autonomous adjustments, however. The onboard inertial guidance and flight control systems compensated for the lower thrust conditions. Its closed loop guidance system measured the decreased thrust in real time and revised the trajectory and burn durations to ensure the mission succeeded. The GPS IIF-3 satellite was delivered to the correct orbit as planned.

United Launch Alliance has begun an investigation into the incident.

December 10, 2012