[X] My Assistant

[djellison]

Indeed - the AmSat DL team at Bochum with their 20m dish that's just 1/15th the diameter of Arecibo received a signal almost 2 months ago

http://amsat-uk.org/tag/bochum/

[Mongo]

A minor update: a comment today to this article about the recontact attempt.

We are here at Arecibo and we hope to get our newly arrived Power Amplifier installed today and we are getting ready to attempt our first commands!

[Paolo]

from an email just sent to supporters:

some late-breaking news: during our listening sessions at Arecibo the other day it became clear to us that the ISEE-3 spacecraft is not exactly where JPL's database said it would be. After several decades, this is understandable. By adjusting the big dish we determined that the spacecraft is roughly 250,000 km from where is should be. Given that it is already on a lunar flyby trajectory - a close one at that - the error is such that there is a chance that it could hit the Moon - unless we fire the engines - and do so rather soon. All the more impetus to get things up and running! We're in both Reboot AND Rescue mode now!

[mcaplinger]

One wonders how much of this is a real concern and how much an attempt to increase drama. The latter would be understandable but I look forward to the technical details.

[Explorer1]

http://spacecollege.org/isee3/isee-3-reboo...nnis-wingo.html

First commands may be sent as early as Tuesday....

[Phil Stooke]

So... the lunar flyby was supposed to be very low altitude, and the current uncertainty means the spacecraft might impact. "This has become extremely important as there is a solid statistical chance that the spacecraft could impact the moon or even be off course enough to threaten other spacecraft in Earth orbit."
(http://nasawatch.com/archives/2014/05/isee-3-is-not-e.html)

Is it inappropriate of me to wish for an impact so I can mark it on my map? Not even if I said it was to save those other spacecraft?

Phil

[mcaplinger]

The stated error is 250e3 km, presumably derived from RA/dec errors in pointing since they don't have any range data. Unless there's some data they haven't described, they really know very little about the actual positional error, and prognosticating impacts or approach distances is nearly meaningless at this point. They need ranging, and for that they have to command the spacecraft AFAIK.

[nprev]

"...off course enough to threaten other spacecraft in Earth orbit..."

Oh, come ON. That's off-scale unlikely & quite unnecessarily dramatic. My odds of winning the lottery three times in a row are probably better than ISEE-3 colliding with an Earth-orbiting spacecraft.

[djellison]

Agreed - it's a laughable suggestion.

[mcaplinger]

it's a laughable suggestion.

Laughable probably isn't quite fair. For example, a lot of effort was spent on collision avoidance for the Juno flyby, a lot more than you might expect statistics to justify. But given the lack of knowledge of the trajectory, it's certainly premature to worry.

Now they're saying that they are waiting for NASA approval to transmit (which seems odd). I don't know if they have to explicitly command to get ranging or if the spacecraft will transpond just with an uplink carrier.

http://trs-new.jpl.nasa.gov/dspace/bitstre...2/1/07-0166.pdf is a good reference for how ranging works. I don't know if they have access to the needed ground hardware or if they can fake it with SDR or if this is one of the things they're trying to pay for the DSN to do.

As an aside, orbit determination could be done without any ranging data (Gauss managed it in 1801 after all, see http://www.schillerinstitute.org/fid_97-01...orbit_ceres.pdf ) but I suspect that this would not be accurate enough to support their navigation goals.

[djellison]

Yes - but Juno was coming to within a few hundred km of Earth - thru the shell of comm HEO, MEO, LEO spacecraft - thousands and thousands of active and tens of thousands of deceased bits of hardware. That is deserving

ISEE-3 with possible lunar flyby or lunar impact? Using words like "threaten other spacecraft in Earth orbit" - that's laughable. There's as much chance as a random asteroid taking out an earth orbiting spacecraft

[ElkGroveDan]

Good point Doug. It sounds like a bunch of self-serving hype if you ask me.

[Paolo]

according to the latest tweet by the ISEE3 Reboot Project

we are go to contact #ISEE3 this afternoon

according to JPL's horizons, ISEE-3/ICE will be close to the zenith at Arecibo around 19.45 UTC

[Explorer1]

They got it! (for real this time)

[Paolo]

SUCCESS!!! http://spacecollege.org/isee3/we-are-now-i...spacecraft.html