Reading the significant events report for 6th December, it appears that there will be a 10-day period next year where Cassini data may be lost due to the Phoenix requirement for DSN coverage during entry, descent and landing at Mars.
This is unfortunate as it appears that the actual landing (25th May 2008) of Phoenix occurs during periapse for Cassini. There are good flybys of Pallene, Atlas and Janus on that day (whether observations of these are planned or not, I'm not sure) but the Titan flyby on 28th May should be unaffected
The significant events report states possibly 50% data loss over the ten days.

Of course, Phoenix should definitely take priority...

What with sometime heavy rain over Madrid and the increasing number of missions though, I propose a large relay station at our L2 lagrange point

Speaking of loss of coverage, is one of those 70m antennas still under "scheduled maintenance"?

Stupid question probably, but are there no other radiotelescope facilities worldwide that NASA could 'hire' to cover special circumstances like this, where the problem is anticipated well in advance?

While the technical idea is appealling to three additional surface stations for the DSN - one in South Africa\Namibia\Botswana, one in Chile\Argentina\Uraguay and one in Japan\Korea\Russia would provide significant redundancy and weather independance and would be vastly cheaper to build and maintain than an L2 relay.

Just my 2cents.

I was wondering about that as well. DSS on a boat covering the double-booked antennas would be even cooler. Of course, boats probably aren't steady enough.

There's the ESTRACK dishes at Cebreros and New Norcia that could assist - but they'll probably be on-call for MEX for the Phoenix EDL relay.

Doug

Some more??
http://www.r-clarke.org.uk/astrolinks_radio.htm

This is a good point Helvick - it's easy for me to blithely suggest billion dollar space relays...
I imagine that over the next couple of decades, the resources of the DSN will become increasingly stretched though, and how tragic would it be if we lost even 5% of the data from New Horizons for example, due to adverse weather conditions on Earth.
The idea of an expanded earth-based network is an appealing one (especially if we're talking fractional cost against space-based) I just wonder if this would remove all future data priority conflicts. I would hate to have to be the one to make a decision to lose say, a 50km Enceladus remote sensing flyby, a Mercury magnetometer survey, or a Pluto occultation.

While we're being blithe, why not stick a deep space antenna on the space station?

The only tragedy would be if we lost the Doppler and occultation data. Hopefully such events can be timed to be in view of more than one existing station. Since New Horizons is recording all the data from its instruments and then playing it back over a six month period, the rest of it could just be retransmitted. Such event happened to Voyager-2 at Uranus, which cost data including the only picture of Puck due to a thunderstorm in Canberra, but fortunately it was retransmitted before the tape recorder was needed again.

I Can't remember what was the antena that picked up Spirit signal before the DSN. So, it has been done, may be as a backup only.

I think you might be thinking of the UHF transmission from Spirit to MGS, which MGS-MOC ( i.e. Mike C ) was trying to tell the control room had picked up a long enough signal to be certain of a happy landing...but they didn't listen.

Doug

There may be issues with the lead time on this one, but it's been done in the past. NASA paid to put a set of receivers on the VLA antennas to support the Voyager 2 Uranus/Neptune encounters, and the Parkes 70-meter dish as well (which has a long and continuing history of spacecraft tracking, even if it was a standin for a smaller one in "The Dish"). Radio astronomy tends to use broader bands in different spectral spots than spacecraft communication, which accounts for needing different receivers (although NASA has a history of leaving behind very nice low-noise receivers which are just crying for other uses). The other large dishes that would be worth checking on would be Arecibo (as wailing and gnashing of teeth are heard; I think Saturn will be within its declination limits although for only about an hour a day), the ~110-meter Green Bank telescope and the 100-meter at Effelsberg, plus maybe the 14x25-meter Westerbork array.

The VLA staff have been working up the case for how tracking can be improved using long-baseline interferometry, which gives very pleasant accuracy in a direction different from what you get from Doppler and ranging measurements.

This culled from the Cassini-Huygens significant events report from December 6th last year (as mentioned above):

"Members of the Target Working Teams (TWT) met with Mission Planning to discuss the impact of the Phoenix Entry, Descent, and Landing (EDL) period on DSN support for Cassini. Unfortunately, the Saturn TWT orbits 64/65, or 2008-138T04:20:00 to 2008-148T04:43:00, along with the other TWTs and Orbiter Science Teams (OST) had planned extensive observations for that time frame and will be losing a good deal of planned 70m station coverage. In particular, EDL is on the day of periapse, closest approach to Saturn. Since the Aftermarket process for S40 is over on Dec. 6, a discussion of science priorities and data volume cuts - probably about 50% - for that time frame will be the main topic of conversation at upcoming TWT/OST meetings."

Does anybody happen to know which data will be lost in this timeframe??