Arthur T Knackerbracket has processed the following story:
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 [scientists] 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.
(Score: 3, Interesting) by JoeMerchant on Friday March 21, @05:17PM (4 children)
>one facing forward along the space vehicle's trajectory and another identical unit facing in the opposite direction.
Great, and how does the satellite determine which way is forward? If you have a tumbling cube-sat, will six sensors be able to infer "forward relative to atmo" and calculate speed based on that?
>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
I guess by the time you get up to Geo-stationary this isn't applicable.
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(Score: 0) by Anonymous Coward on Friday March 21, @11:17PM (1 child)
Tumbling? They do de-tumbling with their magnetorquers after deployment. It takes a while since the magnetorquers only put out a small force.
(Score: 2) by JoeMerchant on Saturday March 22, @06:22PM
Yes, but how do they know the speed sensor is aligned to the relative atmospheric motion? Law of sines isn't your friend at that orientation.
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(Score: 2) by PiMuNu on Saturday March 22, @04:41PM (1 child)
> I guess by the time you get up to Geo-stationary this isn't applicable.
There's quite a lot of charged particles coming from the sun. Typically you have about one charged particle passing through you every second, indirectly originating from the sun (it's indirect because there is some particle shower in the upper atmosphere). They may be too high energy to be useful for this device as the particle velocity is much higher than satellite velocity, but one might be able to infer direction to the sun using such a device and thus orbital angular velocity.
(Score: 2) by JoeMerchant on Saturday March 22, @06:24PM
I get direction to the sun working, but that is a confound for orbital velocity. I wonder what the windspeed is at geo stationary and if it is solar dominated or still parallel to earth's surface more or less?
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(Score: 3, Informative) by Ken_g6 on Friday March 21, @10:22PM (5 children)
If it works on the moon [nasa.gov], it should work for basically every possible Earth orbit.
I would think that, being above the ionosphere, satellites wouldn't have their GPS signals affected by space weather, but I'm not sure.
(Score: 3, Interesting) by JoeMerchant on Friday March 21, @11:04PM (3 children)
Being the nerds they are, this is for any planet not just Earth. Also, rugged independent thinkers don't like high profile failure points.
Yes, when GPS is available it's cheaper. Except for the cost of launching and maintaining the constellation.
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(Score: 2) by turgid on Friday March 21, @11:16PM (2 children)
I don't suppose there are many atmospheric ions on the Moon?
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by JoeMerchant on Friday March 21, @11:43PM
You would think not, but there are some and the front-rear differential method can probably work quite well even if the atmospheric density varies as you go.
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(Score: 3, Informative) by Username on Friday March 21, @11:46PM
I'm willing to give them the benefit of the doubt, that they over simplified their explanation on the workings of the tech, due to the telephone effect on the transfer of information between different areas of a company. Even on the moon, you will come into contact with more matter on the leading edge than on the trailing. We create a multi plane of sensors, like in the game of jacks, a three dimensional asterix, we can easily detect which direction we are going based on where matter is detected on each end.
(Score: 2) by Username on Saturday March 22, @12:01AM
It's always good to have a backup. If this sensor disagrees with GPS, you know you have a problem.
It is also good for navigation outside of earth's orbit.
Always put the bow into the wave. How do we know where the wave is located? Leading edge of our aerodynamic surface should be pointed at the most amount of matter detected to reduce drag and keep momentum. Are we flying now? is this really space? I have no idea, I just know what I know.
(Score: 2) by jman on Saturday March 22, @11:40AM
Or, another company the Mustelidae can purchase and run into the ground. Wait, they'll run into the ground by themselves eventually, anyway, he could just charge for it and never actually do the upgrade.