DS1 Gets Upgraded and Rebooted

Andy_Howell writes "In the "even spaceships have to reboot departmet," NASA's DS1, which is essentially "software with an ion drive," just got new code. This new software is part of an extension of its mission to investigate Comet Borrelly this September."

Fiber optic Gyros?

[helleman]

Anybody know how those work?

Sounds cool...

Re:Which Hardware

[alispguru]

DS1 is running an RS/6000 (IBM's version of the PowerPC architecture) at something like 25 MHz. That was the fastest rad-hardened chip they could get when they started the design.

The operating system is RTWorks, a Unix-like realtime kernel. The system software is written in C and Common Lisp (for the Autonomous Remote Agent stuff).

For details, check out http://nmp.jpl.nasa.gov/ds1/ [nasa.gov]

Re:Fiber optic Gyros?

[BobGregg]

Via this...
http://www.google.com/search?fibre+optic+gyroscope [google.com]

comes this:
ESA, 1998: New European Gyroscopes for Space [esrin.esa.it]

Which Hardware

[Rentar]

Anyone knows what kind of hardware they use?

I don't think it's an x86 or anything like this. I heard that many satelites use low-tech, 'cause it is more stable.

Anyone got information?

Uh Oh....

[big_groo]

One uses a conventional charge-coupled device detector, the other a new technology detector.

We're doomed. It's using and NT detector. Let's just hope it doesnt explode in a ball of blue and white light.

Re:takes balls

[Pogue Mahone]

MURKY navigation software? Written by MURKYsoft? Ohnoohnoohnoohno...

;-)

Although it could explain why they have to reboot it to take into account the new configuration.

Re:Fiber optic Gyros?

[jovlinger]

But not precise enough to keep orientation for more than a few minutes? Why is that?

Re:Fiber optic Gyros?

[Spamalamadingdong]

Sure. You take a length of glass fiber and wind it around a spool. You take a laser, split the beam and send half into each end of the fiber (or maybe just use the fiber itself as the laser). The light goes around and around and eventually comes out the other end. You take this light and shine it on a screen or set of sensors, where (being coherent light) it forms a diffraction pattern.

If nothing was moving, you'd just see a static pattern. However, if you turn the spool around its center axis the photons going one way through the fiber have to travel a bit longer to get to the end than the photons going the other way. The diffraction pattern shifts, and you can measure this shift.

Look up "laser ring gyro" for more information. Here's a link [fas.org].
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Oops

[Spamalamadingdong]

I meant "interference pattern". Diffraction has nothing to do with it.
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Re:Fiber optic Gyros?

[norton_I]

Yeah, they are way cool.

Basically, you have an interferometer that looks like this:
/--\
||
1--/--/
|
2
where the lower left hand '/' is a beam splitter, and the other /'s and \'s are regular mirrors. Shine a laser in from the left (1), and normally all light comes out the left -- there is perfect destructive interference between the clockwise and counter-clockwise paths to come out port (2).

If you rotate the whole apparatus, you effectively shorten one path and lengthen the other, and from the change in the inteference, you can measure the angular velocity.

Now replace the whole thing with a big loop of fiber optics with a fiber coupler instead of a beam splitter, and you have a light weight, very precise, solid state gyroscope.

Commercial aircraft use these, too.

Re:takes balls

[Spamalamadingdong]

since DS1 had lost its star tracker, it has to use its CCD camera to orient itself. That means it can't keep track of its orientation very well while it is snapping photos of stuff around it anymore.

Yes and no. It can keep track of its orientation in two axes using its sun sensor (which is still working just fine) and its rate gyros (which tell it how fast it is turning). The problem is that the sun sensor doesn't help in the third axis (rotation around the sun-spacecraft axis) and the gyros have a non-zero drift rate.

I've been privy to some of the talk about the development of the MURKY navigation software, and it has been fascinating. The people running DS1 are the créme de la créme of geekdom.
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takes balls

[po_boy]

that's pretty cool. I'm hesitant to reboot a machine with a new kernel on it remotely. I've never had to do it when "remotely" meant 197 million miles away.

The article also mentioned that since DS1 had lost its star tracker, it has to use its CCD camera to orient itself. That means it can't keep track of its orientation very well while it is snapping photos of stuff around it anymore. That's a hell of a predicament to be in, I guess.