Very soon, Mars will appear too close in the sky to the Sun for us to communicate very well to the MERs. Can someone say what the blackout dates will be, and especially when we start communicating again?

Wouldn't that be during the last 3 weeks of October ?

Press releases from last time around may serve as an estimate.
Before:
AfterThe rovers only took images of the sky during those that period, The gap between movements was longer about 18 days.

Wouldn't that be the Mars-Earth-Sun angle? The Mars-Sun-Earth angle should be near 180 degrees.

For MRO with its demostration telecomunications with k-band can work up to 0.5 degree against to 2 degree for X-band.

Rodolfo

It is the angle formed by a line going from Mars to Earth to the Sun, not Mars to the Sun to Earth. Good catch.

The Pioneer 11 Saturn encounter was just before solar conjunction, and communications degraded rapidly after about the time of closest approach to Saturn, forcing them to drop data rates progressively as they moved away from Saturn. With absolutely no onboard bulk data storage, they got what they could in realtime as the spacecraft exited the magnetosphere.

Thanks, so my understanding is that it will be about 18 days, starting in the next few days, and ending before the end of the month.

The 0 degree solar conjunction between Earth and Mars will be at the October 23. See at http://www.above-heavens.com

The reliable X-band communications would be starting after 2 degree from the center of Sun), that is when? : Trigonometry =>

tang(2 degrees) =d/(150,000,000+249,200,000 km from the Sun)
d = tan(2)*399 millones => 13,933,387 kilometers.

Mars orbits around the Sun at the aprox speed of 86,871 km/h.

Hence, the Mars' travel time from 0 to 2 degree of Sun would take = 13,933,387 km/86,871 km/h => 160.39 hours => close to 7 days. I don't know about the difference of 2 days (7 versus 9 days, it might be lead by many unprecise ciphres).

Hence, October 16 (seven days before of Oct 23), the communication with Mars will start to be nill. fourteen days later, at October 31, the telecomunications with Mars will resume.

Rodolfo

Do you know I'm quite pleased about 18 days "downtime"

I need that time to catch up with all the posts you guys have been making in the last 3 days while I've been away from a computer!

Aberdeenastro

What a terrible birthday present!
Well, at least this finally opened near me! I will plan on going during the opposition to hold me over.

I envy you since in Lima we still has no IMAX. Good time on your birthday!.

Rodolfo

Glad we have an IMAX theater in Brussels

Huhhuhhuh, Philco, is it running in Brussels!? I'm in Brussels too!

Here's a day-by-day reckoning of the changing elongation of Mars from the Sun during the black-out period.

Steve

After seeing the above figure and found that my previous calculations (start at October 16 and ends at October 30) are fine!

Rodolfo

I've got the Official answer
From last Spirit update :"This year's solar conjunction period begins on the rover's 991st Martian day, or sol, (Oct. 16, 2006) and ends on sol 1005 (Oct. 30, 2006). Planning for future activities on sols 1006 and 1007 (Oct. 31 to Nov. 1, 2006) will resume Oct. 30."

I can't believe I read plan for 4 digits sols

Amazing 4-digit sols

The end of conjunction date in the Spirit update has changed! Climber quoted that conjunction would end on Oct 30th now the next update says:



Nov 10th, can that really be right?

Good news that they will still be trying to downlink a little.

James

I just noticed that, too. The posted ephemeris data would support the previous update as being correct.

The thing I wanted to ask about was the comment saying there would be daily downlinks during the conjunction. I can see how Odyssey might have a shorter time in conjunction, but surely even it will be blacked out most of the time, wouldn't it?

Edited: On second thought, 15 megabits isn't all that much. I guess they can manage some lower rate communication closer than 2 degrees.

Yeah, from Steve's above post I would say that Oct 30 seems right, the new update must be in error.

I guess there is no harm in trying to transmit data - even if a lot of it doesn't make it through, at least a few scraps should let the engineers know all is well.

Waaaaay too long to post here, but if anyone would like to read it I have written a new poem about Opportunity. Just click on the link below, and let me know what you think - if you want!

"Conjunction's Dream"

I know with MRO, we're planning to start operations around the 8th, so...

That's a useful piece of information. Playing with a protractor in my normally reliable planetarium software, I am going to interpret that date as the conservatively expected onset of reliable communication. I expect good communication somewhat sooner. A guy can hope, can't he?

I think there will be some communication a few days earlier, but, well, MRO does have alot more information to pass to it to do it's work, and we have a bunch of data to download, so... MARCI and MCO are operating. In the end, it'll probably be by the 8th that we can start stuff.

I notice that we do have pictures back from Oppy yesterday. Nothing exciting, but there are pictures.

Yes, Diane, we did. Although they were not terribly interesting, it does seem that some data has trickled in. Tonight I went to JPL's solar system simulator and generated views of the sun as seen from Mars (woops, I mean as seen from Earth). I chose a field of view of 5 degrees, and watched Mars as it and Earth chased one another around the Sun.

The attached gif animation displays the Sun at the center of the 5 degree field of view, so there are 2.5 degrees on either side of the center of the Sun as Mars passes by. By October 31st, it would appear to have gone beyond the nominal 2 degrees of elongation officially quoted earlier, and well past the 0.5 degrees noted as communication limits also officially quoted for MRO, as mentioned by Rodolfo. I enjoyed taking out an old tool I haven't used since I had to draw contour maps by hand, my dividers. By Jove, they still work well as a navigation aid. As far as I can tell from the 5 degree simulator images, these simulator images agree reasonably well with the ephemeris numbers posted by Dave in post #15. An added bonus is a glimpse of Venus and the Messenger spacecraft passing through the scene.

It's also apparent that Mars' orbit as seen from Earth only grazes the edge of the Sun, and isn't totally covered by it. So, what is the story regarding the blackout period for the various Mars missions? I am measuring something like a 5 degree elongation for the November 8-10 dates.
Click to view attachment

There isn't a blackout, at least, not a complete one. Although I can state, there is signifigantly less telemetry than normal from MRO, probably about a tenth or less of the telemetry, it's not a complete blackout, it's just a whole lot harder, that's all. And there are lots of black-out windows as well, which is also quite rare. But, as a whole, well, we are still getting some data, just not that much.

The big mystery was the asymmetry of the conjunction period given in the Spirit update in post 19 above. It's now clear that was in error. According to the new planetary society update, the conjuction period is now over:
A clue to the origin of the error: So the November 10th date may have come from another mission.

http://qt.exploratorium.edu/mars/opportuni...POP2406R2M1.JPG

Nice view of The Beacon, alan. The other one of the small bay is interesting, too. It seems noticeably steeper, and there are a lot of pebbles at the bottom that had me wondering if many of them were berries.

fredk: I think that must be it. There are a number of mission specific limits based on previous conjuctions that did not accurately reflect the conditions in this one. It's nice to see the pipeline opening up again. Whoohoo!

Processed version (this is a geologist heaven!)

Thank you Dilo, yes it really are heaven, strata after strata. All I wished for in Victoria.

Conjunction is definately over now, huge group of pan cam's down

http://nasa.exploratorium.edu/mars/opportu...cam/2006-11-01/