GPS World

Tag: spacecraft

  • NASA advancing GNSS capabilities for spacecraft

    NASA advancing GNSS capabilities for spacecraft

    NASA’s Space Communications and Navigation (SCaN) program is developing capabilities that will allow missions at high altitudes to take advantage of GNSS signals for timing and navigation, including the Artemis missions to the Moon.

    Interoperability of the GNSS constellations will be key for spacecraft at higher altitudes where GNSS signals are less plentiful. The program will rely on the four global constellations (GPS, Galileo, GLONASS and BeiDou) and the two regional systems operated by India and Japan.

    SCaN is supporting flight experiments that will help develop multi-GNSS capabilities for spacecraft, such as Bobcat-1, developed by NASA’s Glenn Research Center in Cleveland and Ohio University.

    Bobcat on the Prowl

    Bobcat-1, shown with its deployable antenna stowed, will experiment with the GNSS inter-constellation time offset from low-Earth orbit. (Photo: NASA)
    Bobcat-1, shown with its deployable antenna stowed, will experiment with the GNSS inter-constellation time offset from low-Earth orbit. (Photo: NASA)

    Bobcat-1 was selected by the CubeSat Launch Initiative in 2018 to study GNSS signals from 250 miles overhead. The small satellite launched to the International Space Station aboard a Northrop Grumman Cygnus spacecraft on Oct. 2, 2020.

    On Nov. 5, the space station released the CubeSat to begin its mission. The spacecraft will orbit for about nine months, measuring signals from different GNSS constellations. Engineers will use these measurements to better understand GNSS performance, specifically focusing on timekeeping variations between the constellations.

    “GNSS users at high altitudes see fewer satellites,” said Bobcat Co-Principal Investigator Frank Van Grass of Ohio University. “Time offsets between the constellations can be measured by the CubeSat and provided to these users to improve their positioning performance,”

    SCaN Testbed

    Bobcat-1 builds on the legacy of the SCaN Testbed, which demonstrated multi-GNSS capabilities on the space station from 2012 to 2019. The GPS and Galileo Receiver for the International Space Station (GARISS) — an instrument developed in collaboration between NASA and ESA (European Space Agency) — received signals from both GPS and Galileo, the GNSS constellation operated by the European Union.

    The SCaN Testbed prior to launch to the International Space Station. (Photo: NASA)
    The SCaN Testbed prior to launch to the International Space Station. (Photo: NASA)

    The SCaN TestBed also laid the foundation for the Lunar GNSS Receiver Experiment (LuGRE), a Commercial Lunar Payload Services payload being developed in partnership with the Italian Space Agency. The payload will receive signals from both GPS and Galileo and is expected to obtain the first-ever GNSS fix on the lunar surface.

    GNSS PNT Policy and Advocacy

    While NASA engineers develop the technologies necessary for multi-GNSS navigation at ever-higher altitudes, the SCaN team works with stakeholders in the U.S. government and internationally to advance GNSS interoperability in the policy sphere. They consult on the United Nations International Committee on GNSS, helping develop additional capabilities in the Space Service Volume and beyond.

    NASA recently worked to publish GPS antenna patterns from GPS satellites that launched between 1997 and 2000, collaborating with the U.S. Space Force, the U.S. Coast Guard and Lockheed Martin, who built the satellites. The PNT team is also working to facilitate publication of antenna patterns for more recent GPS satellites.

    With this data, mission planners can better assess the performance of GNSS in high-Earth orbit and lunar space. This forthrightness also encourages other GNSS providers to be similarly transparent.

    The Goddard PNT policy team received a 2019 Agency Honor Award for their advocacy of NASA’s interests in GNSS. From let are Frank Bauer, Jenny Donaldson, J.J. Miller, Ben Ashman and Joel Parker. Not pictured, Lauren Schlenker. (Photo: NASA)
    The Goddard PNT policy team received a 2019 Agency Honor Award for their advocacy of NASA’s interests in GNSS. From let are Frank Bauer, Jenny Donaldson, J.J. Miller, Ben Ashman and Joel Parker. Not pictured, Lauren Schlenker. (Photo: NASA)

    “GNSS capabilities continue to revolutionize the ways spacecraft navigate in near-Earth space and beyond,” said NASA navigation engineer Joel Parker. “NASA’s longstanding relationships with the GNSS providers have advanced these capabilities to new heights and support the Artemis missions on and around the Moon.”

  • Directions 2021: GLONASS on the verge of a new decade

    Directions 2021: GLONASS on the verge of a new decade

    By Yury Urlichich, first deputy director general of Roscosmos State Space Corporation
    Sergey Karutin, designer general of GLONASS
    Nikolay Testoedov, director general, Information Satellite Systems JSC
    Sergey Koblov, director general, Central Research Institute of Machine Building JSC

    The year 2020 heralds the end of another 10-year stage of development of the Russian GLObal NAvigation Satellite System (GLONASS). Reconstruction of our orbital constellation, started in 2006, is bearing its fruit. Today, it is hard to imagine one’s daily life without the continuous artificial radio-navigation field provided to users globally by the GLONASS orbital constellation since 2011.

    GLONASS signals are employed to perform a wide range of tasks, such as

    • Saving lives in road accidents
    • Air, ground and naval traffic monitoring and control
    • Network synchronization of mobile cellular communications
    • Monitoring and enabling the energy grid, road travel, agricultural equipment operation, and more.

    Our orbital constellation is built upon a base of second-generation spacecraft (SC) — Glonass-M SC — that was developed in 2003 and has demonstrated outstanding operational capacity: 14 SC are already operating well beyond their expected lifetimes, and four SC celebrate their 13th birthday in orbit this year. Activities focused on improving GLONASS accuracy have not stopped for a single day.

    If we go back to 2014, the SC-based ranging offset (which specialists refer as equivalent ranging deviation) was 1.4 m. We managed to achieve 0.9 m offset on Jan. 30, 2020, and during the same week the offset did not exceed 1.15 m. Furthermore, the penultimate series-produced Glonass-M SC (Cosmos-2545), which was launched on March 30, demonstrated basic service ranging accuracy of 0.38 m on a daily interval and 0.63 m accuracy on the “best week” interval.

    Glonass-K No. 15 was launched into orbit on Oct. 25. (Photo: Roscosmos)
    Glonass-K No. 15 was launched into orbit on Oct. 25. (Photo: Roscosmos)

    It was Glonass-M SC development that enabled users around the world to gain access to the first dual-frequency navigation service, which is necessary for decreasing the effects of the ionosphere on navigation accuracy.

    The third generation of GLONASS SC — Glonass-K  — was successfully launched from the Plesetsk launch site on Oct. 25. This SC will provide users with a broader range of capabilities — and a more accurate and informative signal in the L3 frequency band. Further gradual rejuvenation of the GLONASS constellation will ensure the ever-improving quality of our navigation services.

    Two Glonass-K2 SC are planned for the launch campaign in 2021, and all the experience accumulated during the development of third-generation GLONASS SC (Glonass-K) will be implemented in the fourth-generation SС. Glonass -K2 is a unique SC: It will provide users with five navigation signals, its accuracy will be within 0.3–0.5 m, and its assured expected lifetime will be at least 10 years.

    High-Orbit Space Complex

    GLONASS developers remain focused on user requirements. Recent surveys show a growing demand for high-quality navigation services in difficult conditions where the SC is visible at more than 25° above the horizon. To satisfy these needs with the implementation of new CDMA signals, development of the GLONASS High-Orbit Space Complex (HOSC) will begin in 2021. Its first SC will be launched in 2025, and complete deployment of the constellation including six SC in three or six planes will be finished by the end of 2027.

    As a result, the accuracy and availability of navigation in difficult conditions will improve in the Eastern Hemisphere. But the major anticipated outcome of the HOSC implementation is assured two-fold coverage of the Northeastern segment of the globe with high-accuracy differential navigation data by GLONASS and other GNSS.

    HOSC implementation will ensure 25% navigation accuracy improvement over the Eastern hemisphere. Glonass-K SC will be used as a base platform for HASC deployment due to its excellent record.

    Ground Control at the Titov Main Test Space Center established a stable telemetry connection with the new satellite shortly after launch. (Photo: Roscosmos)
    Ground Control at the Titov Main Test Space Center established a stable telemetry connection with the new satellite shortly after launch. (Photo: Roscosmos)

    User Interface Harmony

    One of the most important tasks for the year 2020 is harmonization of the GLONASS user interface. As we already mentioned, the signal propagation environment has a strong effect on navigation accuracy; therefore, new issues of GLONASS Interface Control Documents (ICD) are being prepared for publication.

    We anticipate that GLONASS end-user accuracy improvement will be achieved through introducing additional information into reserve bits of navigation frames, including relevant parameters of an ionospheric model.

    The ICD will contain operating methods with parameters of the ionospheric model and definite recommendations designed for compensation of ionospheric delays by both single-frequency and dual-frequency receivers, as well as generalized methods for compensating for tropospheric delays.

    Changes in the ICD concerning FDMA and CDMA signals will ensure backward compatibility and uninterrupted operation for the existing range of user navigation equipment.

  • Using GPS, NASA tests atomic clock for deep space navigation

    Using GPS, NASA tests atomic clock for deep space navigation

    While in orbit, the Deep Space Atomic Clock (DSAC) mission will use the navigation signals from GPS coupled with precise knowledge of GPS satellite orbits and clocks to confirm DSAC’s performance.

    News from the Jet Propulsion Laboratory, NASA

    In deep space, accurate timekeeping is vital to navigation, but many spacecraft lack precise timepieces on board. For 20 years, NASA’s Jet Propulsion Laboratory in Pasadena, California, has been perfecting a clock. It’s not a wristwatch; not something you could buy at a store. It’s the Deep Space Atomic Clock (DSAC), an instrument perfect for deep space exploration.

    The atomic clock, GPS receiver and ultra-stable oscillator that make up the Deep Space Atomic Clock Payload, following integration into the middle bay of Surrey Satellite US’s Orbital Test Bed Spacecraft.
    (Photo: Surrey Satellite Technology)

    Currently, most missions rely on ground-based antennas paired with atomic clocks for navigation. Ground antennas send narrowly focused signals to spacecraft, which, in turn, return the signal. NASA uses the difference in time between sending a signal and receiving a response to calculate the spacecraft’s location, velocity and path.

    This method, though reliable, could be made much more efficient. For example, a ground station must wait for the spacecraft to return a signal, so a station can only track one spacecraft at a time. This requires spacecraft to wait for navigation commands from Earth rather than making those decisions on board and in real-time.

    “Navigating in deep space requires measuring vast distances using our knowledge of how radio signals propagate in space,” said Todd Ely of JPL, DSAC’s principal investigator. “Navigating routinely requires distance measurements accurate to a meter or better. Since radio signals travel at the speed of light, that means we need to measure their time-of-flight to a precision of a few nanoseconds. Atomic clocks have done this routinely on the ground for decades. Doing this in space is what DSAC is all about.”

    The Deep Space Atomic Clock in the middle bay of the General Atomics Orbital Test Bed spacecraft. (Image: NASA)

    The DSAC project aims to provide accurate onboard timekeeping for future NASA missions. Spacecraft using this new technology would no longer have to rely on two-way tracking. A spacecraft could use a signal sent from Earth to calculate position without returning the signal and waiting for commands from the ground, a process that can take hours. Timely location data and onboard control allow for more efficient operations, more precise maneuvering and adjustments to unexpected situations.

    This paradigm shift enables spacecraft to focus on mission objectives rather than adjusting their position to point antennas earthward to close a link for two-way tracking.

    Additionally, this innovation would allow ground stations to track multiple satellites at once near crowded areas like Mars. In certain scenarios, the accuracy of that tracking data would exceed traditional methods by a factor of five.

    DSAC is an advanced prototype of a small, low-mass atomic clock based on mercury-ion trap technology. The atomic clocks at ground stations in NASA’s Deep Space Network are about the size of a small refrigerator. DSAC is about the size of a four-slice toaster, and could be further miniaturized for future missions.

    The DSAC test flight will take this technology from the laboratory to the space environment. While in orbit, the DSAC mission will use the navigation signals from U.S. GPS coupled with precise knowledge of GPS satellite orbits and clocks to confirm DSAC’s performance. The demonstration should confirm that DSAC can maintain time accuracy to better than two nanoseconds (.000000002 seconds) over a day, with a goal of achieving 0.3 nanosecond accuracy.

    Tom Cwik, the head of JPL’s Space Technology Program (left) and Allen Farrington, JPL DSAC project manager, view the integrated atomic clock payload on Surrey Satellite US’s Orbital Test Bed Spacecraft.
    (Photo: Surrey Satellite Technology)

    Once DSAC has proved its mettle, future missions can use its technology enhancements. The clock promises increased tracking data quantity and improved tracking data quality. Coupling DSAC with onboard radio navigation could ensure that future exploration missions have the navigation data needed to traverse the solar system.

    Technologies aboard DSAC could also improve GPS clock stability and, in turn, the service GPS provides to users worldwide. Ground-based test results have shown DSAC to be upwards of 50 times more stable than the atomic clocks currently flown on GPS. DSAC promises to be the most stable navigation space clock ever flown.

    “We have lofty goals for improving deep space navigation and science using DSAC,” said Ely. “It could have a real and immediate impact for everyone here on Earth if it’s used to ensure the availability and continued performance of the GPS system.”

    DSAC is a partnership between NASA’s Space Technology Mission Directorate and the Space Communications and Navigation program office, a program under the Human Exploration and Operations Mission Directorate. DSAC will launch in 2018 as a hosted payload on General Atomic’s Orbital Test Bed spacecraft aboard the U.S. Air Force Space Technology Program (STP-2) mission.

  • Lockheed Martin invests $350 million in production facility for GPS III, other spacecraft

    Lockheed Martin invests $350 million in production facility for GPS III, other spacecraft

    Preliminary construction is underway on a new, $350 million Lockheed Martin facility that will produce next-generation satellites.

    The new facility, located on the company’s Waterton Canyon campus near Denver, is the latest step in an ongoing transformation, infused with innovation to provide future missions at reduced cost and cycle time, the company said.

    The new Gateway Center, slated for completion in 2020, includes a state-of-the-art high bay clean room capable of simultaneously building a spectrum of satellites from micro to macro.

    Spacecraft now in production at the site include the Air Force’s GPS III satellites (in the GPS III Processing Facility), NASA’s InSight Mars lander, NOAA’s GOES-R Series weather satellites and commercial communications satellites.

    The facility’s paperless, digitally-enabled production environment incorporates rapidly-reconfigurable production lines and advanced test capability.

    It includes an expansive thermal vacuum chamber to simulate the harsh environment of space, an anechoic chamber for highly perceptive testing of sensors and communications systems and an advanced test operations and analysis center.

    The Gateway Center will be certified to security standards required to support vital national security missions.

    “This is our factory of the future: agile, efficient and packed with innovations,” said Rick Ambrose, executive vice president of Lockheed Martin Space Systems. “We’ll be able to build satellites that communicate with front-line troops, explore other planets and support unique missions.”

    “You could fit the Space Shuttle in the high bay with room to spare,”Ambrose said. “That kind of size and versatility means we’ll be able to maximize economies of scale, and with all of our test chambers under one roof, we can streamline and speed production.”

    Lockheed Martin expects the construction effort to employ a total of 1,500 contractors during the three-year construction phase. Lockheed Martin has added more than 750 jobs to its Colorado workforce since 2014, and has about 350 job openings in the Denver area alone.

    Lockheed Martin’s planned satellite integration facility, the Gateway Center, is slated for completion in 2020. (Photo: Lockheed Martin.}

    The building will accommodate that recent growth and new future projects. State and local officials in Colorado have helped strengthen the aerospace industry and foster an environment that helps aerospace companies thrive and grow.

    “Aerospace is an engine of innovation and growth for America, and we’re investing in infrastructure and technology to help strengthen the nation’s leadership in military and commercial space and scientific exploration,” added Ambrose. “We’re transforming every aspect of our operations to help our customers stay ahead of a rapidly-changing landscape. The Gateway Center, coupled with advancements in 3D printing, virtual reality design and smart payloads, will deliver game-changing innovations while saving our customers time and money.”

    Lockheed Martin’s Waterton Canyon campus has been a hub of space innovation since the 1950s, with more than 4,000 employees and a wide range of industry-leading design, manufacturing and test facilities on site.

    Companies selected by Lockheed Martin for the project include Hensel Phelps as the general contractor, Matrix PDM Engineering and Dynavac for thermal vacuum chamber design and construction, and ETS-Lindgren for anechoic chamber design and construction.