bleirer

Only 38% of earth gravity, so that should help.

Sidwalkastronomy Loc: New Jersey Shore

but much much less atmosphere

lautenk2

I can't wait for the helicopter. I read on space.com or somewhere that the pre-flight setup/checkout will take a month or so.

Tommg

Does anyone on this site have any guess as to approximately how long it takes a picture to get from mars to earth? How do they correct for the spinning of the earth in order to receive the picture on earth? What is the composition of the atmosphere on mars? Thanks

lautenk2

Depending on where they are in their orbits, earth and mars are approx. 35 million miles to 250 million miles apart. Right now, about 130,000,000 miles so RF (or light) takes about 12 minutes to make that trip.

I don't understand what you're getting at exactly with your question on correcting for the spinning of the earth to receive. There are fairly complex calculations involving the position of an antenna here and the position of an antenna on mars (or in orbit around mars, or wherever) but that's to figure out exactly where to point the antenna (for weak signals far away, highly directional antennas are used and they must be precisely aimed to work). So long as the antennas are aimed at each other, you can exchange signals. The doppler frequency shift in the RF signal for the velocities involved here is pretty small so not a significant problem.

I don't remember the composition of mars atmosphere, except that it's not especially corrosive or poisonous, but it is very thin. The atmospheric pressure, and more importantly the density, on the surface of mars is about the same as that flying at 100,000 feet altitude above earth. Nobody around here flies helicopters up to 100,000 feet altitude. This will be really interesting.

Tommg

Thanks for the reply. I'm not an engineer or much of a techie so; I envision the rover parked on Mars looking towards the earth and the earth spinning on its axis (and reloving around the sun) would be constantly moving (spinning) and the antenna on earth(stationary antenna) would not necessarily be pointing at the rover's antenna for very long ... so I don't understand how a picture can be sent from the rover when the antennas are miss-aligned very quickly. Plus the signal from a transmitter 130,000,000 miles away has to be very small ... clear as mud?? The helicopter IS going to be interesting.

lautenk2

The antenna controls are computer driven and they update many times per second. Tracking something on mars has the antenna slewing much less quickly than tracking a satellite in Low Earth Orbit (LEO)(100 or 200 miles for example). LEO objects are only in line-of-sight view of any particular ground based antenna for a matter of minutes as a satellite travels from horizon to horizon in that time. So, tracking a LEO object has the antenna moving plenty fast, likely near its maximum design rate. In both cases, the antenna is moving (perhaps not fast enough to see, like the minute hand on a clock for example) continuously the whole time it's operating.

There are different modes of tracking. For initial signal acquisition, the antenna is pointed at where the control system calculates the target to be. After signal acquisition, it's possible to have the antenna point at where the signal is strongest (and there are ways to tell if you're aimed slightly off center and which direction), and then just follow that. This was all much simplified, but true.

My last USAF duty station is now under US Space Force.

BTW, breaking news: Perseverance rover has just reported the helicopter is alive, awake, and having its battery charge topped-up.

Tommg

Thanks again for helping, I enjoy learning new things (new to me, that is). Can't quite get my mind around all the stuff, probably never will, might be able to get the gist of it, however. Must be some incredible low-noise amplifiers involved in the receiving/processing equipment involved receiving in a 103,000,000 mile transmission?

LFingar Loc: Claverack, NY

Rovers have been sending back photos from the Mars surface for over 20 yrs, including some very high resolution shots from the more recent rovers. By any chance have you seen the hi-res photos of Pluto taken by the New Horizons probe? The distance to Pluto is measured in billions of miles, not millions. NASA will have no problems getting hi-res photos and data from Mars.

Tommg

20 years, that's incredible and I have not seen the hi-res photos of pluto, is there a place on the internet that I can access them? Thanks for the information.

tommg

LFingar Loc: Claverack, NY

Here ya go:
https://www.nasa.gov/
Visit the Image and Mission galleries.

Sidwalkastronomy Loc: New Jersey Shore

If I remember from past missions the rover sends signals to a Mars orbiting craft and from therebavk to earth. Earth has a network of antenna spread all over so we are covered all day and night

LFingar Loc: Claverack, NY

That's the way it works. That way the rovers can be equipped with smaller, lighter, and less power consuming radios since they only have to reach an orbiting satellite instead of all the way back to earth.

bluezzzzz Loc: Stamping Ground, KY

Check out this "decisive moment" captured from Mars orbit!

https://mashable.com/article/mars-perseverance-rover-image-parachute/?utm_source=social&utm_medium=facebook&utm_campaign=mash-com-fb-main-link&utm_content=science&fbclid=IwAR1imbaH610WBGclwfWFpuZWxX7KmT0xwAMuUCZ28OrnAOLlB_1XmuEjAvg

Marshall