Space vehicles | Insight are developing will hopefully enhance the accuracy of satellite positioning, improve navigation for interplanetary missions and ensure the success of space exploration,” says Daniele Palaferri, senior scientist at GEM Elettronica and project coordinator of INPHOMIR. The team is developing an advanced optical gyroscope using laser diodes and indium phosphide sensors that integrate optical processing, These photonic integrated circuit (PIC) devices help to reduce size and power consumption, which are both key for space system designs. The team is also developing a brandnew, mid-infrared, frequency modulated, continuous wave (FMCW) Lidar. This is similar to radar, only with laser to create detailed 3D maps of the environment. “Think of a bat’s echolocation system, but for machines like drones and selfdriving cars. Our FMCW is a fancy way of saying the Lidar sends out a continuous laser beam that changes its frequency over time. By doing this it can measure distances very accurately, even if objects are moving,” says Palaferri. “In space missions, this technology can help satellites and rovers navigate and map out unknown terrains with precision. Unlike existing optical gyroscopes and mid-IR Lidar systems, INPHOMIR integrates all photonic components onto a single chip, reducing size, weight and power consumption. This means all parts of a sensor can be combined on a single chip and the overall device can be much smaller. “By addressing big-data challenges through the development of data-fusion and AI algorithms, we aim to create solutions capable of handling massive flows of data.” The multidisciplinary project is coordinated in Italy by GEM Elettronica and will conclude in 2027. The scheme will validate the performance of the PIC devices with new, ultra low-loss waveguides and new, mid-infrared active devices. The first demonstrations of advanced building blocks, such as extremely high-quality factor resonators, narrow line-width quantum cascade lasers and ultra lowpower, sensitive heterodyne detectors at mid-infrared wavelengths will follow. Atomic clocks Navigating in deep space is not a trivial challenge. Using star maps is the natural way forward, but this requires precise timing over long periods of time, and that requires a lot of transmission data, which uses up the batteries. Instead, a highly accurate onboard clock, called a one-way clock, frees up valuable bandwidth and opens up other applications in the deep space network that communicate with space craft. This would allow the network to simultaneously track two spacecraft on a downlink at destinations such as Mars, for example, and nearly double a space mission’s tracking data because it no longer needs to time-share an antenna. At Jupiter, this would yield a 10-15% increase in tracking, and at Saturn 15-25%, with the percentage rising the further a spacecraft travels. Tracking data precision is improved by a factor of 10 by using the DSN’s Ka-band downlink capability and avoids weather sensitivity in the Ka-band. NASA’s Deep Space Atomic Clock is a critical step towards enabling spacecraft to safely navigate independently in deep space, rather than relying on the timeconsuming process of waiting to receive directions from Earth. Launched in June 2019, the clock is being tested in orbit on a spacecraft provided by General Atomics Electromagnetic Systems of Englewood, Colorado. This is a key element of a real-time autonomous navigation system that tracks one-way radio signals on the uplink and, coupled with optical navigation, provides absolute and relative navigation data. GPS data was collected through two years of testing in orbit, and this was used not only for precise clock estimation but also as a proxy for deep-space tracking data in an experiment on deep-space navigation. Careful selection and processing of the GPS Doppler data and limited modelling fidelity representative of deep-space navigation capabilities showed the atomic clock could be used as a navigation instrument in conditions typical for a low-altitude Mars orbiter. Onboard telemetry quantifying the ultrastable oscillator (USO) frequency correction is processed to show the orbit determination performance degradation when using one-way tracking data. The atomic clock was 50 times more stable than those on GPS satellites, and it is also the first atomic clock that is small and stable enough to fly beyond Earth’s orbit. Timing and frequency stability is comparable to the deep space network’s ground clocks and it can make one-way measurements with similar accuracy to two-way tracking data. 79 Uncrewed Systems Technology | October/November 2024 A swarm of air and ground vehicles is planned for exploring Mars (Image courtesy of University of Wuerzburg)
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