Los Alamos boffins invent speedometer for satellites
Scientists at America’s Los Alamos National Laboratory (LANL) in New Mexico say they have developed a Spacecraft Speedometer that satellites can use in orbit to ideally avoid orbital collisions.
Working with the US Air Force Academy, the LANL boffins say they have come up with a novel device capable of determining the velocity of a satellite while it is looping Earth and potentially other planets.
(The lab repeatedly uses the word velocity in its description of the equipment. Velocity is strictly speaking a vector quantity of magnitude and direction, so we’ll assume the eggheads have been able to determine the speed component of a satellite’s velocity vector using this gadget, at least.)
The Spacecraft Speedometer, we’re told, makes use of twin laminated plasma spectrometers, with one facing forward along the space vehicle’s trajectory and another identical unit facing in the opposite direction.
This design is based on the theory that more charged particles will impact the spectrometer that is facing forward than the rear-facing unit, allowing the velocity to be calculated.
“Like a car driving through a heavy rain, the satellite passes through the charged particles, ions and electrons, that comprise the Earth’s upper atmosphere. In the case of the car, many raindrops will hit the car’s front windshield while fewer raindrops will hit the rear windshield. In addition, the raindrops on the front hit the windshield harder,” the research lab explains.
The principle is therefore that many atmospheric ions will hit the front-facing sensor, dubbed the ram measurement because ions ram into it. Fewer ions will be measured by the rear-facing sensor, called the wake measurement. The Spacecraft Speedometer uses the difference in both the number and impact energy of ions collected by the two sensors to provide an in-orbit velocity measurement.
Although only now being disclosed, it seems that a Spacecraft Speedometer has already been deployed to the International Space Station, mounted on the Space Test Program-Houston 5 platform.
Fear of orbital collisions is one reason why the space-borne speedo was developed. The number of active satellites has grown exponentially in recent years to more than 10,000 in 2024, according to LANL.
Space traffic management and orbit sustainability have become critical issues, but a spacecraft’s location and velocity can only be determined by measurements from the ground. The location and velocity data are used in models that precisely predict future orbits.
This latest device can deliver critical velocity data for operations when ground station tracking fails, such as during severe space weather events, according to LANL.
“These measurements are necessary for improving our ability to accurately predict satellite locations so that we can perform maneuvers to avoid other active satellites and debris,” said Carlos Maldonado of LANL’s Space Science and Applications group.
If all this sounds familiar, it’s because LANL recently announced a way of identifying orbiting satellites from the ground, also to help prevent collisions. It involved attaching a small device that flashes out a “license plate number” code.
With this latest gizmo, LANL boffins can not only get a satellite’s license plate, but also its exact velocity. Are orbital speeding tickets on the way? ®
