Talk:Celestial Navigation

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From a chat about celestial nav-

no prob. I had an idea. [9/28/2008 10:01:35 PM] Paul G Graham says: OK? [9/28/2008 10:01:59 PM] Gary Snyder says: Attitude determination will be required for the vehicles. What is required to get a ccd camera to take a picture of the starts at night and what would happen if that was pointed at the sun ? [9/28/2008 10:04:10 PM] Gary Snyder says: well the idea was what about you doing some hacking on the camera ? [9/28/2008 10:04:56 PM] Gary Snyder says: you are one of the best computer hackers (in a good sense) that i know . [9/28/2008 10:05:30 PM] Gary Snyder says: I'll bet we could dig up the algorithms and star charts in open file formats. [9/28/2008 10:05:56 PM] Paul G Graham says: well thank you... [9/28/2008 10:06:17 PM] Gary Snyder says: firs step is see if a star camera needs to burn out in the sun..... [9/28/2008 10:06:20 PM] Paul G Graham says: For a asto navigation device? [9/28/2008 10:06:26 PM] Gary Snyder says: yep. [9/28/2008 10:06:32 PM] Gary Snyder says: also for a lunar compass [9/28/2008 10:07:45 PM] Paul G Graham says: Well, I'd say the camera is easy enough to make sunsafe, [9/28/2008 10:07:55 PM] Gary Snyder says: Still reading about the Apollo computers. really simple, but good. [9/28/2008 10:08:06 PM] Gary Snyder says: sunsafe may be starblind [9/28/2008 10:08:12 PM] Paul G Graham says: And we could build the same think into a pic. [9/28/2008 10:08:44 PM] Gary Snyder says: no we couldn't. embedded controller yes, but there was a bunch of I/O [9/28/2008 10:09:47 PM] Gary Snyder says: Also it was operable from the astronauts inputs. Realize all the nav was don by the ground and position was determined by range to goldstone. [9/28/2008 10:10:27 PM] Paul G Graham says: OK, so we could build the steroid version on my ts-7300. [9/28/2008 10:10:41 PM] Gary Snyder says: Exactly. [9/28/2008 10:10:48 PM] Gary Snyder says: or my TS-7250 [9/28/2008 10:11:25 PM] Gary Snyder says: Another thing in the inertial platform. The mechanical gyros and accelerometers were really expensive and high quality. [9/28/2008 10:11:58 PM] Paul G Graham says: yes, but, are the SS ones precision enough? [9/28/2008 10:12:21 PM] Gary Snyder says: We would need a strapdown system witch would use modern microcomponents. I am also not so sure that the SS one are accurate enough (or precise) [9/28/2008 10:12:27 PM] Gary Snyder says: I can filter for precision. [9/28/2008 10:13:06 PM] Gary Snyder says: Seems like I figured that the $450 unit would last to orbit ie 10 min accurate to 1 degree. [9/28/2008 10:13:34 PM] Paul G Graham says: we need a little more than that, unless you are just talking about boost phase. [9/28/2008 10:14:05 PM] Gary Snyder says: not if the camera works. Camera takes out drift over time. SS units are on line during burns. [9/28/2008 10:15:10 PM] Paul G Graham says: Ahh, I get it... [9/28/2008 10:15:14 PM] Gary Snyder says: The Apollo computer didn't do strapdown nor the celestial fixes. the astronuats had a sextant and manually entered the corrections (well sort of manually, they told the computer the star and hit a button on a electronic sextant when the start was in the cross hairs. [9/28/2008 10:15:39 PM] Paul G Graham says: right, we could do that in software fairly easily. [9/28/2008 10:15:56 PM] Gary Snyder says: The book is really playing off the astronaut vs automation of the Apollo flights. [9/28/2008 10:16:05 PM] Paul G Graham says: do a sky-wide star chart <-> sky match. [9/28/2008 10:16:35 PM] Gary Snyder says: I haven't finished it, but I really wonder how much can be done autonomously, like the surface rendezvous. [9/28/2008 10:17:07 PM] Gary Snyder says: okay it sounds like you are now the star fix guy. :) [9/28/2008 10:17:07 PM] Paul G Graham says: And tell that camera to never look at the sun, (or earth) and another for high brightness objects... [9/28/2008 10:17:50 PM] Gary Snyder says: I'd prefer to have an inherently good camera that could take a direct hit from the sun, and didn't have any moving parts. [9/28/2008 10:17:57 PM] Paul G Graham says: I'll find someone who actually does that for a living to do it, But I want to make sure we are on the same page 'afore I start writing specs. [9/28/2008 10:18:02 PM] Paul G Graham says: Um... [9/28/2008 10:18:08 PM] Paul G Graham says: Let me do some looking on that. [9/28/2008 10:18:54 PM] Paul G Graham says: It'd be easy enough to do if we didn't mind loosing our star fix during that time, just run an electric welding lens. [9/28/2008 10:19:12 PM] Gary Snyder says: There was a battle in Apollo over the sextant. the MIT lab guys wanted a wide field of view, the spacecraft guys didn't want a door near the heat shield. they wound up moving the vehicle for the second fix. [9/28/2008 10:19:59 PM] Gary Snyder says: Oh I likey. normally dark. slowly bring it up under power to lighten and check for sun. [9/28/2008 10:21:42 PM] Gary Snyder says: okay field of view is still a question. [9/28/2008 10:23:26 PM] Gary Snyder says: An expert in the field would not be able to produce an open source solution. in your position, you could. [9/28/2008 10:23:43 PM] Paul G Graham says: True... [9/28/2008 10:24:12 PM] Gary Snyder says: Then there is the itard question. [9/28/2008 10:24:37 PM] Paul G Graham says: We'll "code" it in Canada. [9/28/2008 10:25:40 PM] Gary Snyder says: open source image mapping and correction software algs would help, or just do the math using a know target. [9/28/2008 10:26:03 PM] Paul G Graham says: Yup, Open source it in any case. [9/28/2008 10:26:08 PM] Paul G Graham says: oh... [9/28/2008 10:26:38 PM] Gary Snyder says: so... the small camera ? [9/28/2008 10:27:37 PM] Paul G Graham says: I'm not so sure wiki's such a good place for code. I need a better code mgr. [9/28/2008 10:27:47 PM] Paul G Graham says: W/ a large FOV. [9/28/2008 10:28:08 PM] Gary Snyder says: Or a security lens for a doorway. [9/28/2008 10:28:26 PM] Gary Snyder says: What about sourceforge ? [9/28/2008 10:28:45 PM] Paul G Graham says: I wonder, one of those 2.5Mp web cams w/ a fish eye lens? [9/28/2008 10:29:09 PM] Paul G Graham says: just put each of the individual projects on sourceforge? [9/28/2008 10:29:12 PM] Paul G Graham says: OK. [9/28/2008 10:29:14 PM] Gary Snyder says: The bigger the megapixel rating, the more work to find the stars [9/28/2008 10:29:28 PM] Paul G Graham says: I guess we don't really need to host everything our self. [9/28/2008 10:29:31 PM] Gary Snyder says: how about an old quickcam. [9/28/2008 10:29:52 PM] Paul G Graham says: I think I'd rather use a new one. [9/28/2008 10:30:03 PM] Paul G Graham says: (They'll give us all we want.) [9/28/2008 10:30:09 PM] Gary Snyder says: no such animal, by flight time they will have changed. [9/28/2008 10:30:40 PM] Gary Snyder says: what do you have. and how is starlight around your house ? we have a streetlight . [9/28/2008 10:30:41 PM] Paul G Graham says: in fact I have an extra last gen orbit here now. [9/28/2008 10:31:05 PM] Gary Snyder says: what about a digikey part ? [9/28/2008 10:31:17 PM] Paul G Graham says: Starlight not so good, often cloudy, but there are some "quieter" places nearby. [9/28/2008 10:31:45 PM] Gary Snyder says: Denver is clear, but well lighted. [9/28/2008 10:32:09 PM] Paul G Graham says: Hey, How about we start breaking some of these projects out onto the wiki? maybe someone is already working this? [9/28/2008 10:33:30 PM] Gary Snyder says: we should start with an equipment page and break out from there. the missions link is a little thin to push people into all the other content deeper.

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