15
$\begingroup$

David Hammen wrote in a comment on Why there is not a single orbiter for Uranus or Neptune? that:

The two Voyager satellites still receive multiple Deep Space Network contacts per week, each of which costs several thousands of dollars to tens of thousands of dollars. Then there are people. The most recent Voyager Space Flight Operations Schedule lists eleven JPL employees. I'd be shocked if a fully-loaded FTE JPL engineer costs less than $250K/yr. Plus there are researchers in other NASA centers and in universities who are supported by the Voyager budget.

Let's go with $10,000 per contact for the Voyagers, via the Deep Space Network, to have a figure in the middle of that range. (If someone has a better estimate, by all means feel free to use that for an answer.) At the low bit rates involved, a contact might last for a few hours. I realize that the equipment is awfully expensive and probably takes a small army of people to maintain, but that still boils down to a few thousand dollars per hour of radio time -- pretty close to a dollar per second. Note that this is in addition to the people actually working to directly support the Voyager missions.

What makes using the DSN so expensive?

A rough costs breakdown would likely make a perfect answer to this question, but a general reasoning could pass as well if it is well-reasoned enough.

$\endgroup$
  • $\begingroup$ What are you interested in, the marginal cost, the average operational cost, the operational cost, the operational + construction ? $\endgroup$ – Antzi Apr 6 '17 at 13:52
  • 1
    $\begingroup$ @Antzi Whichever you feel best illustrates why the cost is so high for the people operating a spacecraft to use the DSN equipment. $\endgroup$ – a CVn Apr 6 '17 at 14:50
19
$\begingroup$

I realize that the equipment is awfully expensive and probably takes a small army of people to maintain, but that still boils down to a few thousand dollars per hour of radio time ...

The cost in 2017 dollars ranges from \$954 per hour of contact for use of a 34 meter High-Speed Beam waveguide antenna to \$4770 per hour of contact for use of a 70 meter antenna, plus charges for an additional hour for setup and shutdown costs. The specific formulae for standard support (see NASA's Mission Operations and Communications Services for details) is

$$\begin{aligned} A_f &= R_b\, A_w\,(0.9 + F_c/10) \\ C &= A_f\, (1 + T) \end{aligned}$$ where

  • $A_F$ is the hourly aperture fee;
  • $R_b$ is the basic hourly fee, \$1057 (2010 dollars);
  • $A_w$ is the aperture weighting:
    • 0.8 for a 34 meter High-Speed Beam waveguide antenna,
    • 1.0 for some other 34 meter antenna,
    • 2.0 for two 34 meter antennae,
    • 3.0 for three 34 meter antennae,
    • 4.0 for four 34 meter antennae, and
    • 4.0 for a 70 meter antennae;
  • $F_c$ is the number of contacts per week;
  • $C$ is the cost per contact; and
  • $T$ is the contact duration in hours.

For example, four two hour long contacts per week with a 70 meter antenna over the course of a year costs \$3.43 million in 2010 dollars, or \$3.87 million in 2017 dollars. Changing those four two hour long contacts per week to one eight hour long contact per week reduces the costs to \$1.98 million in 2010 dollars, or \$2.23 million in 2017 dollars. More frequent short duration contacts are penalized twice, once with the factor $0.9+F_c/10$, and once again with the additional hour (45 minute setup and 15 minute shutdown) per contact.

Why so high? This is very expensive and highly customized equipment. There aren't very many 70 meter antenna in the world. NASA has switched to full cost accounting, which means that projects that use the DSN have to pay for their share of the use of this very expensive equipment. This sharing includes maintenance and upgrade costs.

$\endgroup$
  • $\begingroup$ IIRC contact is scheduled in 8-hour blocks. $\endgroup$ – Hobbes Apr 6 '17 at 14:39
  • 1
    $\begingroup$ @Hobbes - The linked document says that "Note that scheduled pass-lengths should be integer multiples of 1-hour with a maximum of 12 hours per pass." I used two hours as an example. Longer duration contacts would of course cost more. $\endgroup$ – David Hammen Apr 6 '17 at 14:42
  • 8
    $\begingroup$ Right, the cost is not so much the real-time operation those few hours but rather trying to cover some of the maintenance and upgrade costs of the equipment and facilities. The DSN is a finicky combination of very large objects shaped and moved to very high precision with extremely low-noise receivers and high-power amplifiers over several wavelengths, all of which is expected to have 95% or better operational availability for the ever increasing demands of deep space missions. $\endgroup$ – Mark Adler Apr 6 '17 at 18:00
  • 7
    $\begingroup$ @MarkAdler -- Exactly. A Deep Space Network built with low-cost commercially available equipment would suffer a high noise to signal ratio. Inverting this intractable noise to signal problem to a low signal to noise problem means almost everything is either custom or specialized commercial (i.e., custom, but built by someone else). Everything is expensive, touchy, and hard to replace at a moment's notice. Touchy and hard to replace means spares, which increases costs. Reducing noise means a cryogenically cooled preamp at a minimum (in some cases, down to 1.5 kelvins). That's even more cost. $\endgroup$ – David Hammen Apr 6 '17 at 19:23
  • 10
    $\begingroup$ I suspect this answer would be even better if the points made in the previous two comments (@MarkAdler's and David Hammen's) were incorporated into the answer. As it stands, this answer does detail how the cost for DSN time is calculated, but beyond a few sentences doesn't really discuss why the cost is as high as it is, which was my intended focus with the question. The comments do add that aspect. $\endgroup$ – a CVn Apr 6 '17 at 20:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.