NASA Gets a Present

By Julianne Dalcanton | June 4, 2012 10:34 am

The exciting news of the day is that the “National Reconnaissance Office” is donating two unused spy satellites to NASA.  From the limited information available, there are two satellites with 2.4 meter  mirrors just sitting around gathering dust (metaphorically speaking, because they’re actually parked in a climactically controlled clean room). There are no instruments on board, and they lack solar panels or pointing controls, so it will take a fair bit of engineering to turn these into upward-looking space telescopes. In the real world, “engineering” is the same thing as “money”, so the exact fate of these satellites is not clear.  However, it is likely that one will be repurposed into “WFIRST”, which was the Frankenstein-style mission proposed by the latest astronomical decadal survey to provide further observational constraints on Dark Energy.  Many had wondered why no significant funding lines were opening up for WFIRST, but it seems likely that this has been the deep-background plan for a while.  However, WFIRST is only one mission, and there are two satellites, which opens up some exciting possibilities.  I’m sure the UV community in particular is starting to salivate — they’ve been making huge advances in coating and detector technology, so even a modest 2.4m mirror could offer as big a gain as the jump to the James Web Space Telescope (JWST) offers in the infrared.

As someone who spends a lot of time working with the Hubble Space Telescope, this is nothing but good news. The official lifespan of the Hubble is nominally over a few years from now, and the thought of losing generic optical-UV capabilities in space for a decade or more is horrifying.  I’m now much more optimistic that we’ll at least have something up there while we do the hard work of figuring out how to move past the 2.4m aperture size.

The other interesting bit in this for many is the fact that this gift is coming from what is known as the “dark side” — the area of technological development that scientists are not allowed to know about.  The same companies that build major space science facilities (Northrup-Grummond, Ball Aerospace, etc) also build facilities for the military and “reconnaissance” organizations.  The science and military efforts are kept heavily firewalled from each other, of course, but there is frequently a very abstract, high-level of cross talk between the two.  When you’re putting together a project, it becomes clear from the contractor which kinds of capabilities are “easy” (where “easy” means they know how to do it, because of requests from some other government entity).  It is therefore no coincidence that both the Hubble Space Telescope and these unused satellites share a 2.4m mirror, and you can pretty much be assured that some of the expertise used in building JWST either came from or is destined to pass through to the dark side.

 

CATEGORIZED UNDER: Science, Space, Technology
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  • Alex Conley

    What I’m hearing from the WFIRST people is… maybe not so much. Despite how the news stories are spinning it, these satellites are not really wide field in their current configuration. They don’t have tertiary (which therefore would need to be provided), but do have a f/20 secondary. To do wide field for WFIRST, that would have to be replaced, which is not cheap. With all the re-engineering involved, it’s not clear how much that would save. The bigger problem is that the mirrors were not designed to be cold, so that would wipe out the IR component of WFIRST — one of it’s main selling points.

    Still, even if neither turns into WFIRST, it would seem a shame if they didn’t turn into something.

  • Julianne Dalcanton

    Thanks for the insight Alex — I haven’t been following WFIRST closely, so am not sure of the tradeoffs. Maybe that’s what the Euclid investment is — a hedge against losing the IR.

  • Adam Riess

    Actually I understand that the telescope as is *does* offer a wide-field of view, at least 0.25 to 0.5 degree, or 100 times that of Hubble’s instruments. In addition I understand the telescope can be used in the near-infrared just like Hubble. So its not hard to imagine the telescope addressing the science of WFIRST.

  • David Spergel

    Alan Dressler presented a GSFC optical design that has a wide field for this telescope at the CAA meeting today. Without modifying the telescope, we can fit a 0.5 sq deg camera on the “NEW” telescope. NEW = NWNH Enabling Wide-field– the new name for the telescopes.

  • http://lablemming.blogspot.com/ Lab Lemming

    Alternatively, JWST has military-style cost overruns because they can’t borrow aren’t ‘dark’ R&D?

    How much of the total R&D budget is dark research? 75%? 96%? Can we estimate it by the way it alters the trajectory of visible research?

  • Marshall Perrin

    From discussions with some of the optical engineers who’ve been taking a look at this hardware, the “as is” scopes have an unvignetted FOV that is very large, >1º, but the image quality isn’t diffraction limited over that whole field. That can be achieved by adding a new third mirror to make the Cassegrain into a TMA, without having to modify any of the existing optics. The beam isn’t f/20, it’s much faster than that, I believe.

    As for temperature – the WFIRST Science Definition Team interim report envisioned a 240 K 1.3m telescope, so that’s not really cold in the sense of Spitzer, Herschel or JWST. Would a 275 or 290 K scope be that bad, after factoring in the 4x increase in collecting area and 2x better angular resolution?

    Lab Lemming: Total US federal R&D budget is ~55% defense, 45% everything else (but of course, not all of the defense work is dark). See http://www.aaas.org/spp/rd/hist09p.pdf

  • Marshall Perrin

    Ah, the presentations from the CAA meeting today are now online:

    http://sites.nationalacademies.org/BPA/BPA_048755#pastpresentations

  • g

    That’s “Northrop Grumman”, not “Northrup-Grummond”.

  • F. Dufour

    I have a problem with this.

    Mission cost is, very largely, a function of satellite mass. And this was never driven by the optics. This is because of the spacecraft and instruments.

    So, I daresay that it is likely that this mirror would *increase* the cost of WFIRST. Considering the other troubles affecting astronomy budgets, any more money taken out of the Astrophysics theme for this specific mission would spell doom in fiery letters for other specializations. Namely X-ray astronomy and Gamma-ray astronomy. You say that “losing generic optical-UV capabilities in space for a decade or more is horrifying”, then what about us astronomers that can’t observe from the ground?

    Note that I am not a specialist in mission design, merely an informed and interested observer.

  • Jimbo

    No fan of the `Dark Side’, aka military technology, however, there is a wonderful precedent in which highly secretive star wars tech was declassified & handed over to the astronomy community. It was the late `80s, & `adaptive optix’ originally designed to propagate high power laser beams thru the atmosphere w/out degrading, was turned over to astronomers. This technology is now in use at telescopes all over the US.
    I still cannot comprehend how the Webb telly survived congress. Ultimately `built to fail’ as Murphy’s law guarantees, no mission can ever service it, & there must be a zillion glitches that could easily turn it into a multi-Billion$$ piece of space junk.

  • http://mingus.as.arizona.edu/~bjw Ben

    To F. Dufour’s concern: The telescope is the piece of the system that takes the longest time to construct and integrate, and with these things you get an existing telescope and apparently a partial spacecraft bus. That has the potential to save a lot of money not only because you don’t have to buy the telescope, but if the whole process can be speeded up you don’t have to pay the marching armies (including instrument teams) for the time that you save (could be years) during construction. That is my non-expert opinion. Probably the detector array that would go behind one of these things, in a wide-field IR configuration, is similar to the detector array that was planned for WFIRST.

    I agree that the telescope optics do not have to be actively cooled. I don’t think WFIRST was ever intended to have a cold mirror like cryogenic-Spitzer. Warm Spitzer works out to 4.5 microns (in an earth trailing orbit – its heat load would be higher in a orbit around earth I believe).

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  • Patrick M Dennis

    Optical question: I assume these telescopes were designed to focus objects on earth, a few hundred km away. To obtain optimal resolution, would any change be required to image objects in deep space, or is the earth-satellite distance simply “infinity”?

  • https://twitter.com/#!/partialobs Derek Fox

    Hi Julianne,

    Repurposing one of the NEW telescopes for a WFIRST mission, as discussed in Alan Dressler’s NRC presentation and as envisioned by the GSFC design study, would be consistent with the goals and priorities of the “New Worlds, New Horizons” Decadal Survey.

    Repurposing the second telescope as a new optical/UV mission with a funding line beginning this decade would not be consistent with the Survey, so I expect any such discussion would have to join the burgeoning wish list of missions/facilities to be evaluated by the next Decadal Survey in 2019/2020.

    Cheers,
    Derek

  • Julianne Dalcanton

    @Derek — I agree about the destiny of the second scope being not as obvious, in the context of the Decadal survey. What I was envisioning is something where the second scope allows a more significant mission to be brought into a Probe class funding level. The Probes are always competed and are less wedded to the exact Decadal prioritization than the flagships. The Decadal also set up the framework for exoplanets to grab a Probe, and I’d imagine the combination of wide FOV and a coronograph would open up some possibilities for that community.

    @F.Dufour — Yup — the X-ray community is in a tough spot. My understanding is that there are some international missions that can allow progress to limp along, but it’s not like having a large general purpose flagship.

    @LabLemming — I too have wondered if part of the problem with JWST is that it wound up on the leading edge, rather than the trailing. The national security state has a lot more funding to absorb risk, so it’s always better if science follows.

  • Marshall Perrin

    Julianne, I expect you’re right about JWST being on the leading edge. I don’t have any special insights into what’s on those black budgets, but a highly placed Northrup executive, visiting STScI a year or so ago, made a passing remark about “hoping to fly another half dozen of these after this one”, or something like that. On the other hand, the Tinsley factory that made the JWST beryllium mirror segments has been mothballed, so any national security segmented scopes must be planning on a different mirror technology, presumably since cryogenic operation is not a driver.

    @Patrick Dennis: No change is required in the primary or secondary mirrors themselves. The necessary refocusing can be done simply by moving the detector focal plane to a different distance from the mirror. (In fact, many ground based telescopes designed to image at infinity have some sensors focused at a much closer distance, to look at laser guide star spots only 90 km up. Likewise all you have to do is move the detector a bit.)

  • JT

    I agree with F. Dufour. While the NEW telescopes are shiny pieces of hardware, that’s not what drives the cost of the mission. It’s maybe 10% at best. Given that they are LARGER than the original WFIRST proposal, it might actually make the cost INCREASE because of the associated increase in mass from structure, additional optics, etc. It’s like a car dealer offering to give you a free engine on your new $1.5M Bugatti: it is a savings, but that doesn’t mean you can afford to buy the car when you’re still trying to make your yacht (JWST) payments.

  • Mission_guy

    Julianne, et al. — the problem with the idea of using the second telescope for a Probe class mission anytime soon is that, in fact, NO Probe class competed mission line exists within the NASA astrophysics program. There are Explorers at ~100-200M$, and Flagships. There is no funding line, no established program (like New Frontiers for the planetary program), and no real strong will to create such a funded mission line. It’s been talked about, of course — but most folks “probe” concept ideas is just a rebranded $1B flagship.

    Maybe a telescope on the table, however, will be the inspiration needed to create such a line.

  • Chris Hirata

    In response to some of the questions that have arisen:

    @#1 et al: Yes, you need at least 3 curved mirrors to have a corrected wide field of view reflecting telescope. Basically in designing the surfaces there have to be enough degrees of freedom to cancel out all the aberrations at every point in the field with acceptably small residuals. The SDT WFIRST designs have 3 curved mirrors plus several flats (to fold the beam into an acceptable volume). Of course if you’re given the first 2 curved mirrors then you have additional constraints. The solution presented at the CAA handles this with 3 smaller curved mirrors in the camera.

    But closely related to this is the issue of the optimal pixel scale for accomplishing the WFIRST science program if one increases the diameter to 2.4 m. The existing scale (0.18″/pixel) would have to go down since on a 2.4 m telescope it would waste the telescope’s resolution (and the undersampling would negatively affect several science programs). Whether it should go down in proportion to the diffraction spot size, to 0.0975″/pixel, or to some other value is under discussion — this is both a science trade and bears on the surface shape and packaging of the camera mirrors.

    @#6: In the near-IR you are looking at the Wien tail of the thermal emission from the mirrors: this is proportional to their emissivity and to exp[-hc/(kT lambda)]. So if you want this to be small (compared to the zodiacal light, the main irreducible background), changes in the temperature translate into changes in the maximum wavelength observable — the one thing you can’t do is increase the product T*lambda very much, as the exponential gets bad really fast.

    WFIRST originally could observe wavelengths as long as 2 microns, using mirrors at 240 K. Since then our optics engineers have changed the mirror coatings and been able to lower the temperature to 205 K so we can observe out to 2.4 microns. With the NRO telescopes, the 2.4 micron cutoff would get shorter again. (The slides in Alan’s talk had 2.175 microns, where the thermal emission is significant but not fatal, if the camera is designed to be colder than the telescope). So some wavelength coverage is given up but it’s certainly still “infrared”.

    Related, @#11: No active cooling is contemplated in any WFIRST option I’ve studied — as long as you have a sunshade and can radiate into space the shaded components can get really cold (in fact you heat them above their equilibrium temperatures so that you can actively control the temperature, usually a good idea with precise optical components).

    @#13,16: An object is “at infinity” for the purposes of focusing if it is farther away than ~D^2/(2lambda), or about 3000 km at 1 micron wavelength. So depending on what this thing was originally supposed to do … :) But unless the object is really really close, moving the secondary (or detector) would be sufficient to refocus. The issue is not really relevant to this discussion though, since we don’t have the originally planned back-end optics (see above).

    @All: What would it cost to use the NRO hardware (relative to the current WFIRST designs), and what improvements in the science could be realized by going up to a 2.4 m telescope? This work is ongoing now (some preliminary calculations were already presented at CAA!) so I think a lot more will be known relatively soon.

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  • Robert Kirshner

    My name for this is GHOST: Gift Horse Optical System Telescope.

    This also resonates with “spook” and is appropriate for something that has come through the wall from the dark side.

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