But this is useless unless those UHF systems are configured to allow commanding of the spacecraft. And, for that matter, unless they are turned on.
No spacecraft, so big, relies on a single communication unit. All of them have, beside high frequency high gain antenna, UHF or VHF systems all the time.
It simply does not make sense to send the spaceship just with an active X band antenna and later using it to activate the UHF module, the backup, which is slow but much more reliable than a dish antenna, because it can communicate in any condition and at any orientation.
Mars Rovers have also UHF modules and this is the emergency antenna. In the first moments on the surface it is this antenna that send and receives data not the high gain one.
"each rover carries 3 much smaller antennas — one that can move in different directions called the high gain antenna, and two others that are fixed — the low gain and Ultra High Frequency (UHF) antennas. When a rover uses the high gain antenna to speak directly with Earth, it is important that Earth be in view of the rover. That's because this type of communication is a direct shot to Earth, so Earth must be above the martian horizon. The high gain antenna must also be in the correct position. It can spin around so that the entire rover doesn't have to waste energy twisting and turning to get in the right orientation to face Earth. However, in the first few hours of the mission, before the high gain antenna is up and running, the low gain (low-bandwidth) antenna is put into action. Again, Earth must be above the martian horizon as the low gain is also a direct-to-Earth communicator. But the low gain antenna does not have to be pointed at the Earth. Its signal is sent out in all directions at once. We say it’s “omnidirectional”.
see: http://athena.cornell.edu/kids/bn_special_report.html
The fact that Russians do not have UHF like mars rovers and many other spacecrafts is simply not credible. Just to rely on the self capabilities of a dish antenna to orient itself to the earth is simply irresponsible. Only and idiat could have designed such a spacecraft.
For JimO’s equator crossing from the southwest, the satellite is initially pulled to the west and, after the equator crossing, pulled back to the east. So, I’m thinking, there is no change in the plane of the orbit.
UHF is not used for deep space.
JimO back -- that's the operative statement: "they still could not leave immediately". Waiting for orbital precession will see the Earth-Mars window CLOSE before the planar window re-opens.
Waiting for orbital precession will see the Earth-Mars window CLOSE before the planar window re-opens.
Would you mind providing some actual numbers to support this conclusion since you're willing to call all chances of doing so "totally BOGUS"?
UHF is not used for deep space.Yes it is, as an emergency system. I gave you the example of Mars Rovers. Sorry, but you look to be in denial.
UHF is not used for deep space.Yes it is, as an emergency system. I gave you the example of Mars Rovers. Sorry, but you look to be in denial.
Why would it need to precess 360 degrees?
Why would it need to precess 360 degrees?Orbit precession means see this pictures. Only after 360 degree you have the initial situation.
Why would it need to precess 360 degrees?Orbit precession means see this pictures. Only after 360 degree you have the initial situation.
UHF is not used for deep space.Yes it is, as an emergency system. I gave you the example of Mars Rovers. Sorry, but you look to be in denial.
You are wrong. I can't help if you interpreted data wrong. The Mars Rovers low gain antenna is X-band and not UHF. You have an agenda and facts will not change your mind.
Sure, but why can't you shoot off of the bottom (decending node) rather than the top (ascending node)?
Sure, but why can't you shoot off of the bottom (decending node) rather than the top (ascending node)?Even if you accelerate, using the engines, to the perigee you will finally escape earth gravitation while the spacecraft is traveling in the apogee direction if you want to stay fuel efficient.
Sure, but why can't you shoot off of the bottom (decending node) rather than the top (ascending node)?Even if you accelerate, using the engines, to the perigee you will finally escape earth gravitation while the spacecraft is traveling in the apogee direction if you want to stay fuel efficient.
For JimO’s equator crossing from the southwest, the satellite is initially pulled to the west and, after the equator crossing, pulled back to the east. So, I’m thinking, there is no change in the plane of the orbit.
You ARE getting it. The orbital plane's inclination to the equator does not change, but its position in inertial space has slightly twisted to the west. The path after the equator crossing is parallel to, but offset to the left from, the path WITHOUT the effect of the orbital bulge extra mass.