The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory

[Serow225]

Very cool, I worked with one of the engineers who did the stress & airflow analysis for cutting that big hole in the plane, it was really interesting to hear his stories! And yes, as goodcanadian stated elsewhere in this thread, there are airflow management modifications in front of and behind the door to make this all possible.

[netcraft]

I wonder if the plane flies during the day or night? I would assume that for a given mission its one or the other, which makes me also wonder how fast or slow it flies. Even though it is looking in the infrared - wouldn't the daylight still affect it?

[goodcanadian]

We only fly at night. Well, technically speaking, we can observe with the sun up, but the guider cameras are optical which makes it nearly impossible to track any targets when the sky is bright. Moreover, we have to stay well away from the sun as the telescope would focus the sunlight with enough intensity to destroy itself. So, yeah, we only fly at night.

Airspeed is roughly mach 0.85.

[dylanrw]

During one of my many Lyft rides I learned the driver was also one of several managers on this project. We had an interesting chat about it, and it left me wishing that the people involved in this sort of work were paid substantially more.

[john_b]

Agreed, unfortunately meaningful projects such as this are not a high priority for the US electorate (and thus the US Congress) [1]. My hope is that growing interest by college students in STEM subjects [2] will ultimately lead to an increased understanding of the importance of these projects in the long term.

[1] http://en.wikipedia.org/wiki/Budget_of_NASA

[2] https://www.stemconnector.org/sites/default/files/store/STEM...

[dnautics]

oh interesting. I'm also a lyft driver/scientist. I'm doing a series of in-car interviews of scientists, I'd love to try to talk to him, would you be able to contact me (details in profile)?

[nawitus]

How long are the exposures? One would think that due to vibration etc. the exposures need to be extremely short, but long exposures are beneficial in astrophotography.

EDIT: Wikipedia answers the vibration issues: http://en.wikipedia.org/wiki/Stratospheric_Observatory_for_I...

[astrobokonon]

Vibration isn't the reason why exposures tend to be short, and at the longer wavelengths SOFIA operates at it's not the dominant source of the image quality. The real reason is that at the infrared wavelengths seen on SOFIA the sky that we're looking through is very bright, and can quickly saturate detectors.

If you're interested in the nitty-gritty (with pictures!) there's a PDF that describes one of the methods: http://www.sofia.usra.edu/Science/instruments/FORCAST_observ...

Edit: More nitty-gritty here: https://www.sofia.usra.edu/Science/ObserversHandbook/FORCAST...

[goodcanadian]

There have been a couple of good answers with regard to exposure time. With regard to vibration, the telescope is floated on an oil bearing and gyro stabilized. It is well isolated from aircraft vibrations.

[greglindahl]

It's normal to take many short exposures and stack them up to get a long one. The length is dictated by the amount of noise in your detector. From a look at the Wikipedia article, it looks like they need a lot more than just short exposures on Sofia.

[ddrmaxgt37]

My favorite 747! It's the 747SP. I love how short and fat it looks.

[aunty_helen]

Here is one of the runs they did last year: http://flightaware.com/live/flight/NASA747/history/20130717/...

The arches are when they are doing their observations.

Edit: For some reason the map is centering over the Atlantic when I open the link, the flight path is actually from New Zealand if you can't see it to start with.

[valarauca1]

I wonder how it'll compare to eventually to be launched James Webb Telescope.

[privong]

At wavelengths which they both observe (~1–28.5 microns; SOFIA goes out to longer wavelengths than JWST), JWST will be far superior in terms of both sensitivity and resolution. For one, the mirror on SOFIA is less than half the diameter of that on JWST ([0],[1], so the resolution is less than half as good and the collecting area is down by more than a factor of four). Even though SOFIA flies above a lot of the infrared-absorbing atmosphere, it still suffers from some absorption. Additionally, the aircraft and the remaining atmosphere emit in the infrared, so the background levels for SOFIA are much higher.

That being said, SOFIA operates at far-infrared wavelengths as well, which JWST will not support. There are satellite missions being propose which would work in the far-infrared; none have been fully approved yet (to my knowledge), but any of them would surpass SOFIA in most metrics (except perhaps spectral resolution).

[0] http://www.sofia.usra.edu/Science/telescope/index.html

[1] http://jwst.nasa.gov/faq_scientists.html#whatis

[ra]

There's a fantastic BBC Horizon documentary called, "Seeing Stars" which includes, among other things, a SOFIA mission: http://www.dailymotion.com/video/x1kacli_bbc-horizon-2011-se...

[rosser]

Opening that door must do abysmal things to the plane's drag coefficient.

[goodcanadian]

As I understand it, opening the door has negligible effect on the performance of the aircraft. The shape of the fuselage is modified to send airflow past the aperture.

[qwerty_asdf]

  The telescope on board is 10 times as sensitive 
  and has triple the resolution of NASA’s Kuiper 
  Airborne Observatory, originally launched in 
  1975 on a converted C-141 military cargo plane, 
  and decommissioned in 1995. That telescope was 
  the first to spot the rings around Uranus.

"...the rings around Uranus."