Global Positioning News

Tag: IRNSS

  • NovAtel Supplies Reference Receivers for IRNSS Ground Segment

    NovAtel Supplies Reference Receivers for IRNSS Ground Segment

    The NovAtel G-III reference receiver.
    The NovAtel G-III reference receiver.

    NovAtel Inc., a manufacturer of GNSS precise positioning technology, has announced an agreement with the Indian Space Research Organisation (ISRO) to supply reference receiver products for use in the Indian Regional Navigation Satellite System (IRNSS) ground segment.

    India-based Elcome Technologies Pvt. Limited, a sister company to NovAtel in the Hexagon Group of Companies, will provide local integration, training and technical support services for the NovAtel receivers.

    These receivers are based on NovAtel’s G-III reference receiver platform, the same platform used for the Third Generation WAAS Reference Receiver (WAAS G-III), which will monitor the GPS signals for the FAA’s modernized Wide Area Augmentation System network.

  • The System: IRNSS Signal Close up

    IRNSS Signal Close up

    By Richard Langley, Steffen Thoelert, and Michael Meurer

    The spectrum of signals from IRNSS-1A, the first satellite in the Indian Regional Navigation Satellite System, as recorded by German Aerospace Center researchers in late July, appears to be consistent with a combination of BPSK(1) and BOC(5,2) modulation.

    Figure 1 shows that, centered at 1176.45 MHz, the signal has a single symmetrical main lobe and a number of side lobes characteristic of the signal structure that the Indian Space Research Organization (ISRO) announced would be used for IRNSS transmissions in the L-band. Figure 2 shows the corresponding IQ constellation diagram. Further analysis will be required to sleuth additional signal details as ISRO, so far, has not publicly released an IRNSS interface control document describing the signal structure in detail.

    Figure 1. Spectrum of IRNSS-1A L5 signal.
    Figure 1. Spectrum of IRNSS-1A L5 signal.
    Figure 2. IQ constellation diagram of IRNSS-1A L5 signal.
    Figure 2. IQ constellation diagram of IRNSS-1A L5 signal.

    The German scientists caution that “this is a very early snapshot of the current signal transmission and probably both the signal power and the signal quality will change and possibly improve during the in-orbit-testing phase of the satellite’s operation.

    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 contellation.

    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 onboard the space vehicle. When the satellite passes  into the Sun’s shadow behind the Earth, it runs on batteries. The batteries can be re- charged 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 intial 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.

    System Briefs

    GLONASS Partial Make-Good. Russia will launch two GLONASS satellites later this year to make up for the loss of three satellites in the July 2 Proton rocket explosion. The first is scheduled for the beginning of September, and the second at the end of October. Both will rise aboard Soyuz carrier rockets, which have proven more reliable than the Protons. A constellation of 29 GLONASS satellites is now in orbit, with 24 spacecraft in operation, three spares, one in maintenance, and one in test flight phase.

    Meanwhile, plans to reduce GLONASS funding have alarmed at least some deputies of the Duma, the Russian state legislative body. Government officials have floated a plan to reduce funding of the space program in 2014 by 11.7 billion rubles ($355 million), by 13.5 billion rubles in 2015, and by 40 billion rubles in 2016. The federal space program of Russia for 2006-2015 already lacks 10.5 billion rubles funding, and this year there has been a 2.3-billion-ruble additional reduction in R&D. A Duma committee chairperson warned that this trend will “lead to the loss of confidence of the international community in the GLONASS system and, consequently, to a reduction in its use globally. Russia will lose a strategic global instrument of political and economic prestige.” The Duma has recommended that the government maintain funding of federal space programs.

    Galileo Satellites’ Trial By Noise. The first Galileo Full Operational Capability (FOC) satellite successfully completed acoustic testing in July, part of a full-scale test campaign at ESA’s ESTEC Test Centre in Noordwijk, the Netherlands.

    The satellite was placed in the Large European Acoustic Facility (LEAF), effectively the largest sound system in Europe. A quartet of noise horns embedded in a wall of the 11 x 9 x 16.4 meter test chamber generated an acoustic noise level of 140.7 decibels, about the same noise as standing 25 meters from a jet taking off, and intended to simulate the extreme environment experienced by a satellite atop a rocket about to fire itself off the launch pad.

    A second FOC satellite arrived at ESTEC on 9 August from manufacturer OHB in Bremen, Germany. It will undergo a similar acoustic testing and then a System Compatibility Test Campaign will linking it with the Galileo Control Centres in Germany and Italy and ground user receivers as if it were already in orbit.

    A total of 14 FOC satellites are being produced and then tested at ESTEC as an integral part of their path to orbit. A second work order of eight satellites has been given to OHB.

    GPS III Pathfinder. On July 19, Lockheed Martin delivered a full-sized, functional prototype of the next-generation GPS satellite to Cape Canaveral Air Force Station to test facilities and pre-launch processes in advance of the arrival of the first GPS III flight satellite.

    The GPS III Non-Flight Satellite Testbed (GNST) paves the way for the first flight GPS III satellite, expected to arrive at the Cape in 2014, ready for launch by in 2015.

    An innovative investment by the Air Force under the original GPS III development contract, the GNST has helped to identify and resolve development issues prior to integration and test of the first GPS III flight space vehicle (SV-01).

    Following the Air Force’s rigorous “back-to-basics” acquisition approach, the GNST has gone through the development, test and production process for the GPS III program first, significantly reducing risk for the flight vehicles, improving production predictability, increasing mission assurance and lowering overall program costs.

    Lockheed Martin is currently under contract for production of the first four GPS III satellites (SV 01–04), and has received advanced procurement funding for long-lead components for the fifth, sixth, seventh and eighth satellites (SV 05–08).

    GNSS Industry Survey. Here are the results of two questions asked about government and industry from the 2013 GNSS STATE OF THE INDUSTRY SURVEY.

    Is government committed to private industry in a time of drastic budget cuts? For more results from the 2013 GNSS STATE OF THE INDUSTRY SURVEY.
    Is government committed to private industry in a time of drastic budget cuts?
    Is industry actively making its concerns known to government?
    Is industry actively making its concerns known to government?

     

  • Out in Front: A Star Is Born

    Welcome to the club, India, and happy Birth Day. With the July 1 launch of IRNSS-1A, India and the Indian Regional Navigation Satellite System have officially joined the GNSSS (Global Navigation Satellite Systems Society).

    With full membership, however, come some society duties and responsibilities. Chief and first among these is to provide all other society members and interested parties with an interface control document (ICD) defining the characteristics of the signal transmitted from one’s satellites to navigation receivers on the specified radio frequency(ies).

    IRNSS signal transmitters will operate in L5 band (1176.45 MHz) and S band (2492.028 MHz). The system targets provision of an absolute position accuracy of better than 10 meters throughout the Indian landmass and better than 20 meters in the Indian Ocean, as well as a region extending approximately 1,500 kilometers around India.

    Who needs an ICD now, you ask? Who wants to navigate the Straits of Hormuz or New Delhi’s traffic jams using one satellite? No one, of course.

    But nearly every GNSS product developer, designer, and manufacturer has a vested interest in quickly getting their hands on such a document, if they want to sell goods in India, a market of very significant size. Development, design, and manufacture cycles are long, especially when you begin with new and unknown quantities such as a new signal in space. IRNSS once posted a very aggressive schedule: beginning in 2011, it planned to launch two satellites per year, to achieve a full constellation of seven by the end of 2014. Of course, it has fallen a bit behind that curve with first launch in 2013. This would push its operational date to end of 2016. Not all that far out.

    As our OEM editor Tony Murfin wrote last year in a BeiDou context, developers are building digital signal processing application-specific integrated circuits with so-called generic reconfigurable channels to accommodate future add-ons — but RF front-end hardware and signal processing software still require lengthy research and development. Generic DSP channels and associated software decoding algorithms may not be generic enough for all the things that  might await in new modulation schemes yet to come online.

    So it’s not just rabid intellectuals like the Noble New Brunswegian, my friend, colleague, and GNSS mentor and our intrepid Innovation columnist, who prodded me up on this bully pulpit  to ask: O India, where is thy ICD?

    The world’s breadth and depth of GNSS wants to know.

  • The System: IRNSS Success, GLONASS Bellyflop

    IRNSS Success

    The Indian Regional Navigation Satellite System (IRNSS) successfully launched its first satellite on July 1 from the Satish Dhawan Space Centre at Sriharikota spaceport on the Bay of Bengal. An Indian-built Polar Satellite Launch Vehicle PSLV-C22, XL version, carried the 1,425-kg satellite aloft.

    IRNSS-1A is the first of seven satellites that will make up the new constellation: four satellites in geosynchronous orbits inclined at 29 degrees, with three more in geostationary orbit. IRNSS-1A is one of the geosynchronous satellites.

    Following launch, the master control facility conducted five orbit maneuvers to position the satellite in its circular inclined geosynchronous orbit (IGSO) with an Equator crossing at 55 degrees east longitude. Reports indicate that orbit-raising maneuvers have been completed, and all the spacecraft subsystems have been evaluated and are functioning normally.

    IRNSS-1A’s drift eastward from 47 degrees east longitude on July 10 was gradually slowed, and the satellite achieved its assigned inclined geosynchronous orbit, with a 55-degree East equator crossing, by July 18. The orbit inclination is 27.03 degrees.

    Payloads. IRNSS-1A carries two types of payloads, navigation and ranging. The navigation payload will operate in L5 band (1176.45 MHz) and S band (2492.028 MHz), using a Rubidium atomic clock. The ranging payload consists of a C-band transponder that facilitates accurate determination of the range of the satellite. IRNSS-1A also carries corner-cube retro-reflectors for laser ranging. Its mission life is 10 years.

    GLONASS Bellyflop

    A Russian Proton-M rocket carrying three GLONASS navigation satellites crashed soon after liftoff on July 2 from Kazakhstan’s Baikonur cosmodrome. About 10 seconds after takeoff at 02:38 UTC, the rocket swerved, began to correct, but then veered in the opposite direction. It then flew horizontally and started to come apart with its engines in full thrust. Making an arc in the air, the rocket plummeted to Earth and exploded on impact close to another launch pad used for Proton commercial launches.

    Despite the loss, GLONASS still has a full operating constellation of 24 satellites.

    The crash was broadcast live across Russia. Fears of a possible toxic fuel leak immediately surfaced following the incident, but no such leak has been confirmed. The rocket was initially carrying more than 600 tons of toxic propellants. No casualties or damage to surroundings structures or the town of Baikonur have been reported.

    The crashed Proton-M rocket employed a DM-03 booster, which was being used for the first time since December 2010, when another Proton-M rocket with the same booster failed to deliver another three GLONASS satellites into orbit, crashing into the Pacific Ocean 1,500 kilometers from Honolulu.

    A Russian government investigation revealed that at least “three of six angular rate sensors [on the booster stage] were installed incorrectly,” to be specific, upside-down. Examination of the wreckage discovered traces of forced, incorrect installation on three sensors. Assembly-line testing at the factory failed to detect the faulty installation.
    Several videos of the crash are viewable online (YouTube).

    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.

  • Indian Regional Navigation Satellite Starts Signal Transmissions

    Indian Regional Navigation Satellite Starts Signal Transmissions

    By Richard B. Langley

    Update (July 29, 2013): The spectrum recorded by the German Aerospace Center researchers appears to be consistent with a combination of BPSK(1) and BOC(5,2) modulation. This is the signal structure that ISRO announced would be used for IRNSS transmissions in the L-band:

    “The IRNSS signals consist of two special services namely Standard Positioning Service (SPS) and a Restricted Service (RS) [that] will be carried on L5 and S bands. The SPS will be modulated by a 1 MHz BPSK signal and RS will use BOC(5,2) modulation.”

    (“Spectral Compatibility of BOC(5,2) Modulation with Existing GNSS Signals” by S.B. Sekar, S. Sengupta, and K.Bandyopadhyay in Proceedings of IEEE/ION Position Location and Navigation Symposium (PLANS) 2012, Myrtle Beach, SC, April 23–26, 2012, pp.886–890, doi: 10.1109/PLANS.2012.6236831.)

    Scientists from the German Aerospace Center’s Institute of Communications and Navigation in Oberpfaffenhofen, Germany, have received signals from IRNSS-1A, the first satellite in the Indian Regional Navigation Satellite System.

    Launched on July 1, 2013, the satellite reached its designated inclined geosynchronous orbit by July 18 with an inclination of 27 degrees and an equator crossing of 55 degrees east longitude. Indian Space Research Organisation (ISRO) chairperson Dr. K. Radhakrishnan announced on July 18 that testing of the satellite’s navigation payload would begin within a week.

    On July 23, the German Aerospace Center scientists pointed their 30-meter dish antenna at Weilheim towards the satellite and found that it was already transmitting a signal in the L5 frequency band.

    FIGURE 1. Spectrum of IRNSS-1A L5 signal.
    FIGURE 1. Spectrum of IRNSS-1A L5 signal. Source: Richard B. Langley

    Figure 1 shows the spectrum of the received signal. Centered at 1176.45 MHz, the signal has a single symmetrical main lobe and a number of side lobes characteristic of a spread-spectrum signal. The corresponding IQ constellation diagram is shown in Figure 2. The signal structure appears to be unlike those used by the GPS, GLONASS, Galileo, or BeiDou constellations. Further analysis will be required to sleuth the signal details as ISRO, so far, has not publicly released an IRNSS interface control document (ICD). ICDs characteristically describe a satellite system’s signal structure in detail.

    FIGURE 2. IQ constellation diagram of IRNSS-1A L5 signal.
    FIGURE 2. IQ constellation diagram of IRNSS-1A L5 signal. Source: Richard B. Langley

    The German scientists caution that “this is a very early snapshot of the current signal transmission and probably both the signal power and the signal quality will change and possibly improve during the in-orbit-testing phase of the satellite’s operation.”

  • IRNSS-1A Reaches Preliminary Destination Orbit

    News courtesy of CANSPACE listserv.

    Following the July 1 launch of the Indian Regional Navigation Satellite System 1A satellite, five orbit maneuvers were to be conducted by the master control facility to position the satellite in its circular inclined geosynchronous orbit (IGSO) with an equator crossing at 55 degrees east longitude.

    Reports indicate that orbit raising maneuvers have been completed with a fifth apogee motor firing on July 6 at 16:57 IST or 11:27 UTC. All the spacecraft subsystems have been evaluated and are functioning normally.

    The satellite was reported to be in IGSO with a 27 degree inclination at 44 degrees east longitude.

    NORAD/JSpOC has released a two-line element set for the IGSO of the satellite with an epoch of a few days ago:

    1 39199U 13034A   13189.83931637  .00000103  00000-0  00000+0 0    55
    2 39199 027.0197 141.0618 0046168 179.3431 315.7902 01.00666774   276

    This data indicates that the sub-satellite equator crossing was about 47 degrees east longitude at the reference epoch. The satellite orbit equator crossing is drifting eastwards and should reach 55 degrees east longitude by about July 14.

  • India Launches First Navigation Satellite

    India Launches First Navigation Satellite

    News courtesy of CANSPACE Listserv.

    The first satellite of the Indian Regional Navigation Satellite System (IRNSS) was successfully launched today.

    The launch of IRNSS-1A occurred on schedule at is scheduled for 18:13 UTC from the spaceport of Sriharikota. Liftoff from the first launch pad at the Satish Dhawan Space Centre occurred on schedule at 18:11 UTC. The 1,425-kg satellite was launched by the XL version of India’s rocket PSLV-C22, or Polar Satellite Launch Vehicle.

    Solar panel deployment was confirmed and the satellite has power and is operating nominally according to reports.

    The IRNSS-1A satellite is the first of seven that will make up the IRNSS. The constellation will consist of four satellites in geosynchronous orbits inclined at 29 degrees, with three more in geostationary orbit. IRNSS-1A is one of the geosynchronous satellites, and is expected to be positioned at a longitude of 55 degrees east.

    Here is a video of the launch:

    Download a brochure about the IRNSS-1A here.

    NASA Spaceflight provides a summary of the launch.

  • India’s First Navigation Satellite to Lift Off Today

    India’s First Navigation Satellite to Lift Off Today

    News courtesy of CANSPACE Listserv.

    Launch of the first satellite for the Indian Regional Navigation Satellite System (IRNSS) is scheduled for 18:13 UTC on July 1. Launch rehearsal has been completed successfully. The 64-hour countdown is expected to start at 7:11 (IST) tomorrow, June 29, and the launch will take place from the spaceport of Sriharikota. The 1,425 kg satellite will be launched by the XL version of India’s rocket PSLV-C22.

    The status of the launch is updated on this Indian Space Research Organization status page.

    The Chennaionline website is reporting more details here.

    Download a brochure about the IRNSS-1A here.

    For more photos in addition to the above, visit the Indian Space Research Organization website.

  • The System: Galileo Leaves the Building

    In the early hours of May 15, Galileo’s first full operational capability (FOC) satellite left manufacturer OHB System AG’s integration hall in Bremen, Germany, after successfully completing integration and system testing. Later that same day, it arrived by road at the European Space Agency’s (ESA’s) technical center at Noordwijk in the Netherlands for a rigorous set of tests to check its readiness for launch. The tests will simulate different aspects of launch and space environment. The comprehensive test program will validate the new design and all the FOC satellites to follow.

    This first FOC satellite is functionally identical to the first four in-orbit validation (IOV) satellites already in orbit, but has been built by a separate industrial team. Like the other 21 FOC satellites so far procured by ESA, the satellite’s prime contractor is OHB System AG, and the navigation payload was produced by Surrey Satellite Technology Ltd. in Guildford, UK.

    Thermal vacuum testing at the European Space Research and Technology Centre (ESTEC) will simulate temperature extremes the satellites must endure in the airlessness of space throughout their 12-year working lifetimes. Without any moderating atmosphere, temperatures can shift hundreds of degrees from sunlight to shadow.

    Other activities on the schedule include shaker and acoustic noise testing — simulating the vibration and noise of launch — as well as electromagnetic compatibility and antenna testing, placing the satellite in chambers shielded from all external radio signals to reproduce infinite space and check that its various antennas and electrical systems are interoperable without harmful interference.

    “The Galileo FOC satellites provide the same capabilities as the previous IOV satellites, but with improved performance, such as higher transmit power,” explained Giuliano Gatti, the head of the Galileo Space Segment Procurement Office. “They are to all intents a new design that requires a full checkout before getting the green light for launch.”

    The second FOC flight model is due to arrive at ESTEC in early June, and the third in the middle of July. The first two satellites are to be placed in orbit on board a Soyuz launcher, with a scheduled lift-off from Kourou in French Guyana this fall, with two more due to follow by the end of the year.

    The first four Galileo IOV satellites, launched in 2011 and 2012, were provided by EADS Astrium with Thales Alenia Space Italy responsible for integrating the satellites and Astrium in Portsmouth, UK, providing the navigation payloads. They provided their first navigation fix in March 2013.

    The definition, development and in-orbit validation phases of the Galileo programme are being carried out by ESA and co-funded with the European Commission (EC).

    The subsequent FOC phase is managed and funded by the EC. The commission has delegated the role of design and procurement agent to ESA for the FOC phase. At the same time as the satellites are being assembled on a production-line basis, ground stations are also being established on European territories around the globe.

    Photo credit: Pat Corkery, United Launch Alliance.
    Photo credit: Pat Corkery, United Launch Alliance.

    GPS Leaves This Earth

    A t 5:38 p.m. Eastern Daylight Time (21:38 UTC) on May 15,  the fourth GPS IIF satellite, Space Vehicle Number (SVN) 66 built by Boeing, ascended towards orbit aboard a United Launch Alliance Atlas V rocket at from Cape Canaveral Air Force Station, Florida.

    “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 Bernie Gruber, director of the U.S. Air Force Space and Missile Systems Center’s GPS Directorate.

    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 deliver improved anti-jam capabilities for warfighters and improved security for military and civil users around the world, the Air Force said in a statement.

    The IIF-4 satellite is expected to complete testing in August, after which it will be utilized as a reserve or backup satellite. It becomes the fourth satellite in a 12-strong network of GPS IIF spacecraft manufactured by Boeing as lead contractor, the first of which was boosted into orbit in May 2010. The Air Force expects the first of the next-generation GPS IIIA satellites to enter service sometime in 2014.

    System Briefs

    GLONASS. The GLONASS 747 M-series satellite launched on April 26 has maneuvered into an orbital slot near GLONASS 728, the operational satellite in Plane 1, slot 2. 747 will presumably serve as a reserve until it replaces 728, unless another Plane 1 satellite expires first. The next Russian launch, a GLONASS-M trio, is scheduled for July 1. There are currently 24 operational GLONASS satellites.

    IRNSS. The first Indian Regional Navigation Satellite System satellite is expected to rise at the end of June. The IRNSS plans to orbit of seven: three geostationary and four geosynchronous, providing regional coverage via navigation signals in the L5 and S bands.