NuSTAR launches into orbit!

By Phil Plait | June 13, 2012 10:44 am

At 16:00 UTC June 13, 2012, the NuSTAR X-ray observatory began its successful journey into orbit! The satellite was launched using a Pegasus rocket, a smaller vehicle that is literally dropped from an airplane and blasts away into space. This method saves a huge amount of fuel by starting the rocket a few kilometers above the ground. [The image shown here is from a different Pegasus drop and is for explanatory purposes; I'm hoping to get some nice images of the actual NuSTAR launch soon.]

NuSTAR (NUclear Spectroscopic Telescope Array) is designed to detect high-energy X-rays emitted by some of the most violent objects in the Universe: exploding stars, matter falling into black holes, and magnetars (super-magnetic neutron stars that are capable of fierce blasts of energy).

X-ray astronomy is a lot harder to do than regular-old visible light astronomy. For one thing, our air absorb X-rays, so we have to launch telescopes into orbit to see these objects at all.

For another, at these high energies, it’s not possible to focus X-rays in a normal way. Photons of visible light bounce off of mirrors, so we can focus them to a point and see distant objects clearly. X-rays are different, though. Think of them as little bullets zipping along; if they hit a mirror they’ll penetrate right through it! So instead of using a reflective mirror, X-rays can be focused by letting them graze against a gently angled sheet of metal, like skipping a rock on the surface of a lake.

So X-ray observatories like Chandra, XMM-Newton, and NuSTAR use very long cylindrical mirrors. But not precisely cylinders; they gently taper at one end a bit like a thimble. X-rays graze these cylinders and bounce at a shallow angle, coming to a focus. The problem with this is that the angle is so shallow it takes a long path (called the focal length) to get the X-rays to a focus. So the telescopes have to be many meters long.

However, to fit on the diminutive Pegasus rocket, NuSTAR has to be only 2 meters long. Engineers solved this length problem in a very cool way: an extendable boom, like an accordion, that expands after launch and lengthens the spacecraft to over 10 meters! At one end of the extended mast are the mirrors, and at the other end are the detectors, as in the drawing above.

I’ll note I worked on NuSTAR a few years back. When I was at Sonoma State University we developed educational activities based on NASA missions. We were asked to work on the original proposal for NuSTAR to NASA, so my boss Lynn Cominsky and I wrote the original Education and Public Outreach part of the proposal, and once it was accepted I wound up writing a lot of the verbiage for the NuSTAR educational website as well.

NuSTAR has a bit of a checkered history. I wrote about this a while back; in 2006 NuSTAR was abruptly canceled just before the final proposal was submitted to NASA (and I was, um, fairly angry about that), then reinstated a year or so later. But now NuSTAR is in orbit after a wonderfully perfect launch, and I’m very, very happy.

My congrats to the NuSTAR team, especially to Dr. Fiona Harrison — to the best of my knowledge the first female Principal Investigator of a NASA astrophysics mission — on finally getting this important mission into space and peering at some of the most interesting objects in the Universe!

Image credits: NASA/JPL-Caltech/Orbital; NASA/JPL-Caltech


Related Posts:

- Anniversary of a cosmic blast
- NuSTAR revived!
- An Open Letter to NASA

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science, Space

Comments (37)

  1. Steve

    Shouldn’t the word ‘detectors’ be near the ‘optics’ in the above illustration? Or am I reading something wrong?

  2. Kevin

    The Pegasus launch system seems like a great cost-saving design.

    How come we don’t use it for lots of launches?

  3. @Steve, the diagram is correct – the X-rays have to travel the whole ~10 meters from the optics (mirrors) to the focal plane (detectors) before they’re in focus. Since we’re in space, they have no trouble making the journey even though they’re not protected by a telescope tube or other structure.

    -Derek

  4. Carlos

    @Phil – not likely to get better pictures. It was a night time launch, and there was no chase plane.

  5. Carlos

    @Steve – no the picture is right. See Phil’s explanation about the folcal length “So the telescopes have to be many meters long.”. The “Optics” are the focusing mirrors, the “detectors” are at the focal plane many meters behind.

  6. Mike G.

    Interesting design…

    I wonder what the tidal force is across a 10 meter boom?

    Probably not much, but is it enough that the satellite has to constantly compensate for it to keep pointed anywhere but straight up and down?

  7. buttie

    Phil, there’s at least one more female PI. Amy Mainzer was Deputy Project Scientist for WISE and then she took position of Principal Investigator for the NEOWISE. Extension for WISE mission when it has run out of coolant.

  8. Blargh

    buttie: That acronym gives me strange mental images. :)

    “The moment that satellite walked into my office, I knew there’d be trouble. I wondered what it wanted – Earth observation perhaps, or maybe X-ray telescopy. My shoulder began to itch; a grant application the year before had left me with a painful gunshot wound, a stack of unpaid bills and a healthy respect for NASA’s budget negotiations.
    ‘All right’, I said, taking a half-empty bottle of bourbon out of my top drawer. ‘Park your solar panels in that chair and tell me what this is all about.’”

  9. Calli Arcale

    Kevin — the main obstacle to using Pegasus a lot more is that it’s a medium-lift rocket; it’s limited in the size of spacecraft it can put into space, and most commercial users find it cheaper to team up with a bunch of other satellite operators and buy a larger rocket and a payload adapter that can deploy multiple spacecraft. It’s a nice rocket, though, with a good service record.

    As far as launch pictures, I was watching on NASA TV. They had footage from the cameras mounted on the belly of Stargazer; basically, it 45 minutes of the rocket’s nose, followed by a switch to the rocket’s engine, then the rocket dropping out of sight in under a second, and finishing with a sudden brilliant glare that overwhelmed the camera. So, not much to see. ;-) Still cool, though.

  10. Mr. D

    “I wonder what the tidal force is across a 10 meter boom?”

    The torque for 20m would be 400 mN*m, according to this: http://pcos.gsfc.nasa.gov/studies/rfi/Harrison-Fiona-RFI.pdf

    I’d guess the torque goes linearly for a small mast. So half that.

  11. Chris

    Wow, the energy range goes out to 80 keV. My mouth is watering.

  12. Randy A.

    Phil, are there any substances that will slightly slow x-rays, without blocking them, the way glass slows light even though its transparent? You can see where I’m going with this… Could we build a refracting x-ray telescope?

  13. TheBlackCat

    @ Randy: short answer: no.

    Long answer: yes, but not enough to be useful in this situation. You can only change the angle of a light ray a tiny bit with an x-ray lens, so you need to use a lot of them (hundreds) to focus the light in a reasonable distance, and each lens reduces the brightness of the signal, which is a serious problem for a telescope.

  14. Can grazing-incidence mirrors (like NuSTAR’s) also be used for focusing gamma rays?

  15. Pete Jackson

    @Kevin, Calli: To get into orbit requires an altitude of about 200km and a speed of about 26,000 km per hour. The airplane only supplies about 10 km in height and about 1000 km per hour of speed at most. So, the energetics are reduced some, but not by an enormous amount by dropping the rocket from an aircraft. On the other hand, the 10 km in height eliminates most of the air resistance which is important, but I don’t know how important. And, with an airplane, one can launch in a location and direction on the earth which is optimum for the orbit that is planned.

    One major cost saving, however, by using an airplane is the elimination of a launching pad and all its capital cost and maintenance. All one needs is a suitable airport. Of course, one detail is that to launch a really big rocket will require a much bigger airplane than exists today.

  16. Isaac

    I will add that CREAM has a female PI as well (Eun-Suk Seo from the University of Maryland). It’s a NASA astrophysics mission, just not a space-based one (balloon-borne).

  17. Matt B.

    “But not precisely cylinders; they gently taper at one end a bit like a thimble.”

    You mean they’re sections of paraboloids that are cut far from the focus, right? Whereas normal reflecting telescopes use the part of the paraboloid that’s near the focus.

  18. MadScientist

    Accordian to the dictionary, that should be ‘accordion’.

  19. Chris

    @12 Randy
    Another problem is that most substances are going to be opaque at x-ray energies. The only one which is transparent are the light (low atomic number) elements. Beryllium windows are commonly used in x-ray experiments. Also the index of refraction is very near unity in the x-ray region (In the visible region typical glass is ~1.5) Meaning a very large piece of material would be needed to make a conventional lens.

    http://imagine.gsfc.nasa.gov/docs/science/how_l2/xtelescopes_physics.html

  20. F. Dufour

    @ Matt B:
    No, he literally means cylinders. NuSTAR’s mirrors are slumped from flat glass onto cylindrical quartz mandrels and then forced into a conical shape by gluing them onto computer machined graphite bars. Amazing stuff, really.

  21. Messier Tidy Upper

    Congratulations NuStar team, scientists & engineers! Great news. :-)

    My congrats to the NuSTAR team, especially to Dr. Fiona Harrison — to the best of my knowledge the first female Principal Investigator of a NASA astrophysics mission .

    Doesn’t Donna Shirley – manager of the JPL’s Mars Exploration Program esp. the ‘Sojourner’ rover which landed back in 1997 and subject of a great biography ‘Managing Martians’ ( Broadway Books, 1998) written by her and Danelle Morton count? Guess she’s more leading the planetary exploration area than astrophysics but still.

  22. Ken (a different Ken)

    @Kevin, Calli, Pete: There is a great thread over at NASA Space Forums, where Pegasus’s designer Antonio Elias answers all sorts of questions about the vehicle.

    http://forum.nasaspaceflight.com/index.php?topic=3911.0

  23. Mike G.

    Thanks @Mr. D! The HEX-P experiment writeup was very interesting, too.

  24. JMW

    an extendable boom, like an accordian, that expands after launch and lengthens the spacecraft to over 10 meters!

    Why do I have a mental image of Wile E. Coyote affixing a stick of dynamite to the end of an accordion-thingy, and using it to try to pick off the Road Runner?

  25. Teacher Al

    “Accordion” is the correct spelling. The schwa sound gets ‘em every time.

  26. SkyGazer

    Here is the How To Launch A Rocket From A Plane:
    http://www.wired.com/autopia/2012/06/mid-air-rocket-launch/

    (looking waaay back to a previous post from the BA I´m sure he´ll be out again with some RC-friends to do just that and so reviving his youth… and making a guest appearence in Mythbusters.)

  27. Mad Scientist (18), Teacher Al (25): D’oh! Spelling fixed. Funny, I didn’t notice my spellchecker tagging that one. Hmph.

  28. Calli Arcale

    @ Pete Jackson:

    Yes, I think Kevin and I both know that airlaunch doesn’t buy you a whole lot in energetics. Some, but not a lot. He was asking why it is not more used, and I explained that this is because it can only launch smaller payloads, and for commercial operators in that size range, it usually makes more sense to go for a bulk deal on a bigger rocket. It may also be pushing the limits of Orbital’s manufacturing capabilities — I don’t know what their max flight rate is to begin with, and they’ve launched 42 times since their first flight 1990 (including three failures).

    So while I’m not sure what you were responding to with that, you are correct — the main advantage in launching from the aircraft is that you have a much simpler ground support arrangement, and it’s entirely portable to any launch site on Earth that’s within range of a decent-sized airport (one large enough to accommodate widebody airliners).

    You mentioned that a really big air-launched rocket would need a much bigger airplane. That makes me want to plug Stratolaunch, which is aiming to do exactly that. They’re building this monstrous carrier aircraft out of two use 747s. It’ll be this huge twin-boom aircraft (built by Scaled Composites, naturally; they seem to excel at twin-booms) with a Falcon 9 rocket slung in between. It will be rather more limited in where it can operate from, given the size of that aircraft and the use of liquid prop instead of solids, but it’s the same basic concept, scaled up.

  29. puppygod

    Wow, it’s first time I heard about Stratolaunch – and it seems to be pretty neat. This is one of the reasons why I think we should go about commercial space travel. Synergy. When it’s one big government-funded agency, then either they do something or fail. If it is dozen or so smaller entities, each one competing, cooperating and innovating, then even if some fail, other will learn from the mistakes and just a little different approach might succeed. Best luck to them.

  30. Brian Too

    Very interesting info on imaging in the X-Ray band.

  31. I like the launch method. I have long thought that it is a better idea to have a vehicle launch from an aeroplane like first stage.

    I first came across the concept in 1986 when I saw a drawing of a German plan for such a launch vehicle in a series of potential shuttle replacement plans in an issue of Popular Science. A few days later on the morning of January 28th I was discussing the concept with a friend of mine at school as a better idea than the shuttle. I said it was a much better idea than using boosters and a big external tank. Less than an hour later came the news that the Challenger had exploded.

    Creepy.

  32. Gary Ansorge

    Just a note about the European Extremely Large Telescope.. Looks like it will get built…

    http://physicsworld.com/blog/2012/06/one_step_closer_towards_europe.html

    …and that’s way cool too…

    Gary 7

  33. Paul

    One (minor) advantage of air launch is that the first stage engine can have a larger nozzle, and higher expansion ratio. This improves its specific impulse.

    The expansion ratio of a first stage engine is limited by the need for the pressure of the exhaust at the exit plane to not be too low. If it is too much less than ambient pressure, flow separation can occur, with unpredictable (or bad) results. At launch altitude, air pressure is maybe 1/3 of sea level, allowing the nozzle to be longer.

  34. Paul

    A recent paper found a much higher than expected index of refraction at gamma ray energies. So, it may be possible to design a gamma ray telescope with refractive optics.

    http://phys.org/news/2012-05-gamma-ray-optics-viable-tool.html

    (on arxiv: http://arxiv.org/abs/1111.3608 )

  35. @31 Boingo: IIRC, the leading original plan for the Shuttle had it carried aloft by a hypersonic “mothership” that dropped it off at high speed at the edge of the atmosphere. This meant that the entire system was reusable. Unfortunately, they (not sure if it was NASA or some budget committee) decided that designing TWO ground-breaking new vehicles would be too expensive, so they settled on the booster and external tank design (which caused both Shuttle losses). Bummer. If they’d stuck with the original plan, initial expense notwithstanding, the Shuttle might have actually been as cost-effective per launch as was initially advertised.
    On the other hand, hypersonic mothership/daughtership separation (or heck, just a hypersonic aircraft, period) isn’t exactly a well-traveled field, so it may well have been just as risky as the Shuttle design we’re all familiar with. We may never know…

  36. Jonathan McDowell

    Was Nancy Roman ever PI of a mission? She was in charge of all NASA astronomy for a long time especially during the OAO period…

  37. Congrats NuStar Team!! With such past, it is good to see that NuStar is finally launched into its orbit.

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