4 ms·

Still SpaceX routinely recovers the first stage after launching geostationary communication satellites. I thought GPS should be lighter as they are closer to Ea

Still SpaceX routinely recovers the first stage after launching geostationary communication satellites. I thought GPS should be lighter as they are closer to Earth and needs to send much less information in their signal, so the power requirements and size of Solar panels should be lower.

marvin 8y ago
This sattelite was some 8000kgs, vs. 4000-ish kgs for the previous-generation GPS satellites, if I remember correctly.
- Roritharr 8y ago
  Any idea why their weight increased so much?
  - nradov 8y ago
    The latest generation of GPS satellites has more antennas and more powerful transmitters. This improves signal reception and reduces the impact of jamming.
  - walrus01 8y ago
    GPS as received by a small hockey-puck sized antenna is a VERY weak signal, like -140 to -150dB. It only works because the channel size is so narrow and the modulation is very rudimentary. Having a satellite with much larger photovoltaic arrays and really powerful transmitters is one method to overcome regional jamming.
  - tgsovlerkhgsel 8y ago
    I wouldn't be surprised if the satellites had additional, classified capabilities.
inamberclad 8y ago
Looks like GPS-III 3,880 kg at launch. That's fairly hefty, but Falcon 9 has launched other, more massive satellites all the way to GTO (Geostationary Transfer Orbit). The only information I can find on why this one was so energy intensive has to do with the high inclination the GPS satellite has to be in (55 degrees), which is pretty far off from inclination of the launch pad in Florida. Wikipedia says this launch was originally planned on a Delta IV. That would make sense because it has higher specific impulse hydrogen engines. The Falcon does well in LEO, but improved Isp really helps as you go farther out. Here's a video comparing ULA's rockets to SpaceX: https://www.youtube.com/watch?v=QoUtgWQk-Y0 https://www.youtube.com/watch?v=QoUtgWQk-Y0

marvin 8y ago

This sattelite was some 8000kgs, vs. 4000-ish kgs for the previous-generation GPS satellites, if I remember correctly.

Roritharr 8y ago
Any idea why their weight increased so much?
- nradov 8y ago
  The latest generation of GPS satellites has more antennas and more powerful transmitters. This improves signal reception and reduces the impact of jamming.
- walrus01 8y ago
  GPS as received by a small hockey-puck sized antenna is a VERY weak signal, like -140 to -150dB. It only works because the channel size is so narrow and the modulation is very rudimentary. Having a satellite with much larger photovoltaic arrays and really powerful transmitters is one method to overcome regional jamming.
- tgsovlerkhgsel 8y ago
  I wouldn't be surprised if the satellites had additional, classified capabilities.

inamberclad 8y ago

Looks like GPS-III 3,880 kg at launch. That's fairly hefty, but Falcon 9 has launched other, more massive satellites all the way to GTO (Geostationary Transfer Orbit). The only information I can find on why this one was so energy intensive has to do with the high inclination the GPS satellite has to be in (55 degrees), which is pretty far off from inclination of the launch pad in Florida. Wikipedia says this launch was originally planned on a Delta IV. That would make sense because it has higher specific impulse hydrogen engines. The Falcon does well in LEO, but improved Isp really helps as you go farther out. Here's a video comparing ULA's rockets to SpaceX: https://www.youtube.com/watch?v=QoUtgWQk-Y0 https://www.youtube.com/watch?v=QoUtgWQk-Y0