4 ms·

The spy satellite Lacrosse 5 and its “disappearace trick”

81 points by gokhan 12y ago

jgrahamc 12y ago
One night literally lying on the grass in my back garden in Palo Alto I saw a fleet of satellites cross the sky. These were most likely a triplet of NOSS satellites that 'fly' in formation. Wikipedia has a nice picture of these https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_System#/media/File:NOSS-Trio.jpg https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_Syste... and article https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_System https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_Syste...
- lawlessone 12y ago
  wow, I seen that formation as child and freaked out, thought i was looking at a gigantic triangular alien spacecraft.
deanclatworthy 12y ago
There is a link buried on this page that goes into more detail: http://sattrackcam.blogspot.dk/2011/11/lacrosse-5-disappearance-trick-captured.html http://sattrackcam.blogspot.dk/2011/11/lacrosse-5-disappeara... The key questions: > Is it a matter of strongly differing reflectance properties of the satellite body with illumination angle? Is it some brightly reflecting appendage on the satellite disappearing from view? Is it a dark appendage on the satellite starting to block view of the illuminated satellite body, or casting a shadow on it? Is it due to some moving part of the satellite, e.g. a moving dish antenna? It's all rather fascinating. Presumably having a stealth satellite is somewhat redundant as the objects will eventually be seen or tracked by other spacecraft or satellites?
- z303 12y ago
  Well the Misty project did try http://en.wikipedia.org/wiki/Misty_%28satellite%29 http://en.wikipedia.org/wiki/Misty_%28satellite%29
- darkmighty 12y ago
  I'm not sure either, but I believe the orbit of pretty much all satellites is known. You can't conceal a rocket launch, so people know when objects go up and look for them, and comparing to deep space objects you don't need a very powerful telescope to resolve one (but presumably you need good tracking). What's going to be hard is to know the exact purpose of the satellite (so the enemy can't assess you capabilities).
  - ckozlowski 12y ago
    You're right. However, they can still maneuver in orbit. Having a stealth, or low-observable capability allows the operator to "turn the cloaking device on", maneuver the satellite, and potentially get an image of something that would have otherwise been hidden were the orbit known. It has its limitations, of course. But it's a step above a visible satellite with fixed orbit. EDIT: I missed the part where he says it is definitely NOT a stealth capability being demonstrated. So that's not applicable here. Still, a low-observability capability makes sense
    - andor 12y ago
      Satellites are pretty much bound to their orbit once they are launched. They fire their engines only to restore speed (and thus height), and to control rotation. Their speed is such that centrifugal force is in equilibrium with gravity, and most of the kinetic energy is from launching the satellite (with a large rocket). They don't carry enough fuel for arbitrary maneuvers a la Star Trek.
      - ckozlowski 12y ago
        I disagree. Certainly, there's no "arbitrary" maneuvers, "set course", etc. But surveillance satellites will carry maneuvering propellant for a number of reasons: - Station keeping (as you listed) to maintain altitude. LEO satellites will be affected by atmospheric drag. - Assignments - Radar and imagery satellites cannot view everything via a change in rotation alone, and orbital adjustments can be made to the inclination and eccentricity in order to produce an ground track over a target that it didn't follow before. the importance of the target must justify the expenditure in fuel. - Defense - ASATs are a real concern, consisting either of missiles or another satellite steered onto an intercept. Placing one object deliberately onto the path of another is hard enough, surveillance and military satellites will carry propulsion to perform evasion (again, eccentricity, inclination, or altitude adjustments) and mess up a solution. There are no satellites (to my knowladge) that are carrying anything approaching the delta-v required to break orbit, but radical changes in orbit are feasible, and especially for surveillance and reconnaissance satellites, essential.
- danieltillett 12y ago
  Maybe it is one of these systems http://en.m.wikipedia.org/wiki/Kinetic_bombardment http://en.m.wikipedia.org/wiki/Kinetic_bombardment
- ch 12y ago
  Thanks for that link. Very neat how towards the end of the video a Russian rocket booster travels across the frame from right to left. An unintended sighting of some well know space-junk!
  - pavel_lishin 12y ago
    With recent discussions of space debris problems, it's like seeing a rusted out Camaro parked in the middle of Yosemite.
antimagic 12y ago
Background information for anyone not aware, Thierry Legault is a guy that has built a reputation around getting amazing images of various spacecraft in orbit around the Earth. Here's one that he took during last Friday's eclipse: http://apod.nasa.gov/apod/ap150322.html http://apod.nasa.gov/apod/ap150322.html All of which is to say he's one of the foremost civilian experts at imaging satellites from the ground.
- maxerickson 12y ago
  It's worth watching the video of that (link from APOD): https://www.youtube.com/watch?v=JwjvduR3_Ho https://www.youtube.com/watch?v=JwjvduR3_Ho The video is 15 seconds long, the actual transit is less than 1 second.
sandworm 12y ago
Imho this might be an orbital adjustment tool. The thing has solar panels and is in a low orbit. So those panels are a significant source of drag. Normally this is a problem, but perhaps they are using this drag to adjust the orbit. I'm not talking plane change. I mean controlling the amount of drag to adjust orbital speed/altitude/period. Even with all their extra fuel, spy sats do not make plane changes. A significant change would require hundreds of m/s and they have, at best, 1000m/s for their lifetime. (Xenon is power-hungry/tricky/slow and therefore not suitable for quick plane changes). These are multi-billion dollar assets with lifetimes measured in decades. You aren't going to spend 100m/s and shorten the lifetime of the asset by years, effectively spending a billion or more, on a plane change. What they might do is adjust the timing of flyovers by controlled changes to orbital periods. Rotating solar panels, a significant source of drag and reflection, could give some control. Such a maneuver would probably be done at the lowest point in the orbit (highest drag) and could explain the quick and apparently random change in reflectivity. The test for my theory: Does this disappearing trick happen more often at the low point of the orbit? (If you call that the periapsis we know you spend weekends on Duna.)

81 points by gokhan 12y ago

One night literally lying on the grass in my back garden in Palo Alto I saw a fleet of satellites cross the sky. These were most likely a triplet of NOSS satellites that 'fly' in formation. Wikipedia has a nice picture of these https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_System#/media/File:NOSS-Trio.jpg https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_Syste... and article https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_System https://en.wikipedia.org/wiki/Naval_Ocean_Surveillance_Syste...

lawlessone 12y ago
wow, I seen that formation as child and freaked out, thought i was looking at a gigantic triangular alien spacecraft.

deanclatworthy 12y ago

There is a link buried on this page that goes into more detail: http://sattrackcam.blogspot.dk/2011/11/lacrosse-5-disappearance-trick-captured.html http://sattrackcam.blogspot.dk/2011/11/lacrosse-5-disappeara... The key questions: > Is it a matter of strongly differing reflectance properties of the satellite body with illumination angle? Is it some brightly reflecting appendage on the satellite disappearing from view? Is it a dark appendage on the satellite starting to block view of the illuminated satellite body, or casting a shadow on it? Is it due to some moving part of the satellite, e.g. a moving dish antenna? It's all rather fascinating. Presumably having a stealth satellite is somewhat redundant as the objects will eventually be seen or tracked by other spacecraft or satellites?

z303 12y ago
Well the Misty project did try http://en.wikipedia.org/wiki/Misty_%28satellite%29 http://en.wikipedia.org/wiki/Misty_%28satellite%29
darkmighty 12y ago
I'm not sure either, but I believe the orbit of pretty much all satellites is known. You can't conceal a rocket launch, so people know when objects go up and look for them, and comparing to deep space objects you don't need a very powerful telescope to resolve one (but presumably you need good tracking). What's going to be hard is to know the exact purpose of the satellite (so the enemy can't assess you capabilities).
- ckozlowski 12y ago
  You're right. However, they can still maneuver in orbit. Having a stealth, or low-observable capability allows the operator to "turn the cloaking device on", maneuver the satellite, and potentially get an image of something that would have otherwise been hidden were the orbit known. It has its limitations, of course. But it's a step above a visible satellite with fixed orbit. EDIT: I missed the part where he says it is definitely NOT a stealth capability being demonstrated. So that's not applicable here. Still, a low-observability capability makes sense
  - andor 12y ago
    Satellites are pretty much bound to their orbit once they are launched. They fire their engines only to restore speed (and thus height), and to control rotation. Their speed is such that centrifugal force is in equilibrium with gravity, and most of the kinetic energy is from launching the satellite (with a large rocket). They don't carry enough fuel for arbitrary maneuvers a la Star Trek.
    - ckozlowski 12y ago
      I disagree. Certainly, there's no "arbitrary" maneuvers, "set course", etc. But surveillance satellites will carry maneuvering propellant for a number of reasons: - Station keeping (as you listed) to maintain altitude. LEO satellites will be affected by atmospheric drag. - Assignments - Radar and imagery satellites cannot view everything via a change in rotation alone, and orbital adjustments can be made to the inclination and eccentricity in order to produce an ground track over a target that it didn't follow before. the importance of the target must justify the expenditure in fuel. - Defense - ASATs are a real concern, consisting either of missiles or another satellite steered onto an intercept. Placing one object deliberately onto the path of another is hard enough, surveillance and military satellites will carry propulsion to perform evasion (again, eccentricity, inclination, or altitude adjustments) and mess up a solution. There are no satellites (to my knowladge) that are carrying anything approaching the delta-v required to break orbit, but radical changes in orbit are feasible, and especially for surveillance and reconnaissance satellites, essential.
danieltillett 12y ago
Maybe it is one of these systems http://en.m.wikipedia.org/wiki/Kinetic_bombardment http://en.m.wikipedia.org/wiki/Kinetic_bombardment
ch 12y ago
Thanks for that link. Very neat how towards the end of the video a Russian rocket booster travels across the frame from right to left. An unintended sighting of some well know space-junk!
- pavel_lishin 12y ago
  With recent discussions of space debris problems, it's like seeing a rusted out Camaro parked in the middle of Yosemite.

antimagic 12y ago

Background information for anyone not aware, Thierry Legault is a guy that has built a reputation around getting amazing images of various spacecraft in orbit around the Earth. Here's one that he took during last Friday's eclipse: http://apod.nasa.gov/apod/ap150322.html http://apod.nasa.gov/apod/ap150322.html All of which is to say he's one of the foremost civilian experts at imaging satellites from the ground.

maxerickson 12y ago
It's worth watching the video of that (link from APOD): https://www.youtube.com/watch?v=JwjvduR3_Ho https://www.youtube.com/watch?v=JwjvduR3_Ho The video is 15 seconds long, the actual transit is less than 1 second.

sandworm 12y ago

Imho this might be an orbital adjustment tool. The thing has solar panels and is in a low orbit. So those panels are a significant source of drag. Normally this is a problem, but perhaps they are using this drag to adjust the orbit. I'm not talking plane change. I mean controlling the amount of drag to adjust orbital speed/altitude/period. Even with all their extra fuel, spy sats do not make plane changes. A significant change would require hundreds of m/s and they have, at best, 1000m/s for their lifetime. (Xenon is power-hungry/tricky/slow and therefore not suitable for quick plane changes). These are multi-billion dollar assets with lifetimes measured in decades. You aren't going to spend 100m/s and shorten the lifetime of the asset by years, effectively spending a billion or more, on a plane change. What they might do is adjust the timing of flyovers by controlled changes to orbital periods. Rotating solar panels, a significant source of drag and reflection, could give some control. Such a maneuver would probably be done at the lowest point in the orbit (highest drag) and could explain the quick and apparently random change in reflectivity. The test for my theory: Does this disappearing trick happen more often at the low point of the orbit? (If you call that the periapsis we know you spend weekends on Duna.)