[X] My Assistant

[djellison]

http://www.nasa.gov/home/hqnews/2008/dec/H...MSL_Update.html

From the wording of this announcement, MSL is clearly still on, which is a good thing. We'll have to wait and see.

Doug

[dvandorn]

I just went looking for a rate table of DSN fees, and found the following item in a .pdf file ( http://deepspace.jpl.nasa.gov/advmiss/docs...MEX_AO_2007.pdf ) that describes, among other things, the services and rates for the DSN. There was no actual rate chart; there was a formula for calculating what is called the Aperture Fee:

AF = RB [AW (0.9 + FC / 10)]
where:
AF = weighted Aperture Fee per hour of use.
RB = contact dependent hourly rate, adjusted annually ($1057/hr. for FY08).
AW = aperture weighting:
= 0.80 for 34-meter High-Speed Beam Waveguide (HSB) stations.
= 1.00 for all other 34-meter stations (i.e., 34 BWG and 34 HEF).
= 4.00 for 70-meter stations.
FC = number of station contacts, (contacts per calendar week).

The weighting factor seems to be a multiplier based on a function of aperture size (34m vs. 70m) and number of weekly contacts. An accompanying chart shows the weighting factor for a 70m dish used 28 times per week (i.e., 4 times per day), for example, is 15. The same dish used 14 times a week (twice a day) has a weighting multiplier of a little more than 9. The same numbers of weekly contacts using a 34m dish give you weighting mutiplier of 9 for 28 contacts and 2.5 for 14 contacts.

So, a probe that requires four comm passes a day using a 70m dish looks like it would cost something on the order of $15,865 per hour. That's 28 times $15,865 per week, times 52 per year. That would be $444,220 per month, and $23,990,440 per year. That's based on a reading of the chart, not by plugging numbers into the above formula.

A twice-a-day contact through a 70m dish, again based on the chart, would cost $9,500 or so per comm pass, times 14 passes per week ($133,000), for an annual cost of $6,916,000.

And that all assumes that you're only paying for a single hour of DSN time per pass. In actuality, with calibration times, you're likely going to have pay for a minimum of two hours' worth per pass, possibly more (*). So you might have to double those numbers.

However you slice it up between the various data sources coming through on a MODY or MRO comm pass, total DSN costs add up to millions of dollars a year. So I still think one of the biggest chunks (if not the biggest) of mission operations, extended or otherwise, is DSN time.

-the other Doug

* -- the assumption that each comm pass lasts *at least* an hour is built into the rate structure, I think. At least it says in there: "A station contact may be any length but is defined as the lesser of the spacecraft’s view period, the scheduled pass duration plus calibration times, or 8 hours. For a standard pass, a 45-minute set-up and a 15-minute tear-down time must be added to each scheduled pass to obtain the station contact time (other calibration times apply to Beacon Monitoring and Delta-DOR passes). Note that scheduled pass-lengths should be integer multiples of 1-hour." So even if your comm pass only lasts 12 minutes, it doesn't look like you get the benefit of a pro-rate... dvd

[djellison]

So even if your comm pass only lasts 12 minutes, it doesn't look like you get the benefit of a pro-rate...

We've discussed those figures some time ago when talking about discovery missions.

You're not thinking about it properly though - Mars is somewhat unique in that it's almost always locked up with one dish or another. The comms pass will be a 7 hour downlink from MRO and MODY (some of the antennae can and do listen to multiple missions at once) A tiny chunk of that downlink will be MER's - piggybacked on a much much longer session for MODY or MRO. I don't think you can take the generic formula and apply it to MER in that simple a fashion, or indeed any Mars mission. Yes - the DSN costs for MER are not negligible. BUT - they're simply chipping in with a DSN cost that's already there anyway for other Mars missions. The total cost to the Mars Program for DSN costs if you dropped MER would not, I would have thought, drop much, if at all. There's still going to be near continuous downlink from MRO and MODY (and occasionally MEX - although New Norcia and Madrid handle that mostly now). You can't suggest they bill MER for repointing at Mars for each daily downlink when there's a dish already pointing at Mars, and already locked up on the spacecraft that going to do the relay.

Something like Cassini - yeah - take that formula and the schedules and you can find out. The Mars program is more complex than that. How the bill is split up between the missions, we don't know. MER will be paying a lot LOT less than if it were on its own at Mars (which is what your maths infers)