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Orbital debris from India's anti-satellite test? https://www.theguardian.com/science/2019/apr/02/a-terrible-thing-nasa-condemns-indias-destruction-of-satellite

Orbital debris from India's anti-satellite test? https://www.theguardian.com/science/2019/apr/02/a-terrible-thing-nasa-condemns-indias-destruction-of-satellite-and-resulting-space-junk https://www.theguardian.com/science/2019/apr/02/a-terrible-t...

gliptic 8y ago
No, it's extremely unlikely that debris would be propelled from low-earth orbit and hit a tiny satellite over 35000 km away.
sreevisakh 8y ago
Intelsat 29e was in the geostationary orbit at an altitude of 36000 km. The Indian ASAT test was at an altitude of 300km. For any debris to reach that altitude, the explosion has to boost its velocity by 2 to 3 km/s. This is highly unlikely.
- baybal2 8y ago
  For a debris the mass of a screw, it's not that far fetched. Moreover, orbital collision can launch it with an enough velocity to reach GEO orbit retrograde. You need "just" 10 to 15 kJ of kinetic energy. A retrograde collision will then be able to liberate few times more energy. https://instacalc.com/42836 https://instacalc.com/42836 If that happened anywhere close to the apogee of the Indian ASAT test debris, and in same ecliptic, it's very likely it
  - throwaway2048 8y ago
    this would be like throwing a dart at a dartboard on the moon.
  - sreevisakh 8y ago
    That figure of 10 to 15 kJ can be very misleading about what it takes to propel something to such speeds. Put into 'TNT equivalent', it would take the entire energy of 50g of TNT to boost a 100g bolt by just 2 km/s. It's difficult to concentrate that much energy per mass in an explosion (which is leaky). To add further, most ASATs (including the Indian test) doesn't use explosives, but make a direct hit (hit to kill) from a suborbital trajectory (one that has much less energy than an orbital interceptor). The boosting comes mostly from fragmentation mechanics. The satellite will still fragment with some fragments getting boosted up to a higher velocity. In addition, the propellants on the satellite and the kill vehicle might add velocity to the fragments too - though arguably less energy than if it was TNT. So, previous studies on US and Chinese ASAT debris cloud can be considered for a fair assessment. The Chinese test was at a higher altitude of 865km and US test was at a similar altitude. 'Gabbard plot' of these debris show the maximum altitude to be only around 3900 km for both tests. There could be untracked particles at higher orbits, but remember that the velocities of the debris is a random distribution (not sure which one) that tapers at extreme values. Odds of any debris crossing geostationary orbit is very low. There is one additional significant point to consider. Boosted orbits mostly retain the altitude at interception (it's the diametrically opposite part of the orbit that gets affected). This is evident from the Gabbard diagram, where apogee and perigee plots intersect in cross shape with a horizontal line at the altitude corresponding to intercept altitude. This means that most debris come down to atleast 300km. Since the drag at this point is significant, the apogee (maximum altitude) of the debris would decay rapidly - thus mitigating risk to higher satellites. With that odds, a debris crossing geostationary orbit could more likely be from some previous in-orbit explosions than from any ASAT test. Ref: https://sattrackcam.blogspot.com/2019/03/debris-from-indias-asat-test-how-long.html https://sattrackcam.blogspot.com/2019/03/debris-from-indias-... https://sattrackcam.blogspot.com/2019/04/why-even-low-altitude-asat-intercepts.html https://sattrackcam.blogspot.com/2019/04/why-even-low-altitu... https://celestrak.com/publications/AMOS/2007/AMOS-2007.pdf https://celestrak.com/publications/AMOS/2007/AMOS-2007.pdf
    - baybal2 8y ago
      That's a proper argument. I did not think that far
dreamcompiler 8y ago
Not even remotely possible. None of the sources in the India explosion are energetic enough to move debris that high. By a large margin.

gliptic 8y ago

No, it's extremely unlikely that debris would be propelled from low-earth orbit and hit a tiny satellite over 35000 km away.

sreevisakh 8y ago

Intelsat 29e was in the geostationary orbit at an altitude of 36000 km. The Indian ASAT test was at an altitude of 300km. For any debris to reach that altitude, the explosion has to boost its velocity by 2 to 3 km/s. This is highly unlikely.

baybal2 8y ago
For a debris the mass of a screw, it's not that far fetched. Moreover, orbital collision can launch it with an enough velocity to reach GEO orbit retrograde. You need "just" 10 to 15 kJ of kinetic energy. A retrograde collision will then be able to liberate few times more energy. https://instacalc.com/42836 https://instacalc.com/42836 If that happened anywhere close to the apogee of the Indian ASAT test debris, and in same ecliptic, it's very likely it
- throwaway2048 8y ago
  this would be like throwing a dart at a dartboard on the moon.
- sreevisakh 8y ago
  That figure of 10 to 15 kJ can be very misleading about what it takes to propel something to such speeds. Put into 'TNT equivalent', it would take the entire energy of 50g of TNT to boost a 100g bolt by just 2 km/s. It's difficult to concentrate that much energy per mass in an explosion (which is leaky). To add further, most ASATs (including the Indian test) doesn't use explosives, but make a direct hit (hit to kill) from a suborbital trajectory (one that has much less energy than an orbital interceptor). The boosting comes mostly from fragmentation mechanics. The satellite will still fragment with some fragments getting boosted up to a higher velocity. In addition, the propellants on the satellite and the kill vehicle might add velocity to the fragments too - though arguably less energy than if it was TNT. So, previous studies on US and Chinese ASAT debris cloud can be considered for a fair assessment. The Chinese test was at a higher altitude of 865km and US test was at a similar altitude. 'Gabbard plot' of these debris show the maximum altitude to be only around 3900 km for both tests. There could be untracked particles at higher orbits, but remember that the velocities of the debris is a random distribution (not sure which one) that tapers at extreme values. Odds of any debris crossing geostationary orbit is very low. There is one additional significant point to consider. Boosted orbits mostly retain the altitude at interception (it's the diametrically opposite part of the orbit that gets affected). This is evident from the Gabbard diagram, where apogee and perigee plots intersect in cross shape with a horizontal line at the altitude corresponding to intercept altitude. This means that most debris come down to atleast 300km. Since the drag at this point is significant, the apogee (maximum altitude) of the debris would decay rapidly - thus mitigating risk to higher satellites. With that odds, a debris crossing geostationary orbit could more likely be from some previous in-orbit explosions than from any ASAT test. Ref: https://sattrackcam.blogspot.com/2019/03/debris-from-indias-asat-test-how-long.html https://sattrackcam.blogspot.com/2019/03/debris-from-indias-... https://sattrackcam.blogspot.com/2019/04/why-even-low-altitude-asat-intercepts.html https://sattrackcam.blogspot.com/2019/04/why-even-low-altitu... https://celestrak.com/publications/AMOS/2007/AMOS-2007.pdf https://celestrak.com/publications/AMOS/2007/AMOS-2007.pdf
  - baybal2 8y ago
    That's a proper argument. I did not think that far

dreamcompiler 8y ago

Not even remotely possible. None of the sources in the India explosion are energetic enough to move debris that high. By a large margin.