In a message dated Sun, 17 Sep 2000 02:38:04 -0400, JAY RESPLER <jrespler@superlink.net> writes: >> Jim Cook wrote: >> Unfortunately, I'm all thumbs with UTC conversions. > >Seems pretty simple. Not if you're right-brained. ;-) No, seriously, it's not quite that simple, especially if you are not used to working with UTC decimals in the format NASA uses, which I rarely do beyond copying and pasting. You are looking, say, four or five days ahead. You see Heavens-above shows a decent STS-106 pass, say, around 5:30 AM local time. You know NASA is going to make a few orbit changes before then. You have to figure out which UTC number date (259, 262, etc.) applies to the date of the pass, as predicted by H-A, then figure out what the decimal should be. (And then go to the Real Time Data page(s) to see which TLE to use.) >The fraction of a day is constant no matter how many days >there are in a month. They are completely independent of each other. > You usually don't need the exact conversion. Roughly, .1 would be >2.4 hours. .25 (1/4 day) is 6 hours. .5 is 12 hours. That's true, but I, for one, still need to work with them a lot more than I do before the fractions and decimals sink in. And the process is backwards; H-A gives you the rough time, x-days from now, and you have to convert that into NASA's UTC decimal format. >Sue Worden wrote: > >>A "trick" I've used >> for that is to mark up my calendar at the beginning of each year. >> At the top of January goes a "0"; at the top of February goes a >> "31"; at the top of March goes either a "59" or "60". You get >> the idea. The "day" value is then the date in the month plus >> the number at the top of the month, e.g., February 17 is day >> 17+31. > >Ok, here we're talking about day #. I have a little chart that shows # >of each day of year. I can post it on my Sky Views web site (below) if >there's enough interest. Mailed photo copies can be arranged too. Sue, Jay, before anyone goes to any trouble here -- a few things to keep in mind. One is that the, once the final separation burn is completed later today (or early tomorrow), we won't really need to use the Real Time Data TLE's much for the remainder of the STS-106 mission (except perhaps those along the reentry path), so there's no hurry. But I also discovered yesterday that Chris Peat's H-A page -- under the "What Time is It?" link, there's the current date and time, in precisely NASA UTC decimal format (or, as I type this: "Time in two-line element format: 00261.51090278"). Knowing this, it should be much easier to figure out the NASA UTC decimal for a pass a few days into the future. People may still have to do a little figuring, but this gives us a head start. [You would simply add the number of days remaining until the pass to the H-A NASA UTC date. For the decimal, if 1 hour is .04166666667 days (1/24) , then you would round the number of hours of difference between the current hour and the hour of the predicted pass, and multiply that by .04166666667, and then add or subtrack that to the decimal portion of the H-A NASA UTC time. I think ... ;-)] Plus, maybe the best answer to simply approach NASA about the problems many are having using their Real Time Data pages. Perhaps they can add an FAQ (let THEM write this one ;-), or perhaps they could add another JAVA applet to let visitors to their Real Time Data pages enter the Date and Time of an expected pass, (specifying their time zone), and have it compute the corresponding NASA UTC decimal. I think if they knew how confusing those pages can be for a lot of people, they might be amenable to looking into ways to make it easier to use. In a message dated Sat, 16 Sep 2000 18:17:55 -0500, Ed Cannon <ecannon@mail.utexas.edu> writes: >For Jim Cook, here's a page that may include a useful Mac calendar >conversion program: > >http://allmacintosh.xs4all.be/tangerine/calclokmac.html Thanks, Ed. I'll go through those (there must be two dozen or more) and see which look promising. Maybe there's a perfect answer among them. In a message dated Fri, 15 Sep 2000 21:35:33 +0000, Jonathan T Wojack <tlj18@juno.com> writes: >>But then the Real Time Data page, oddly, had replaced the shuttle >>orbit numbers with ISS orbit numbers, confusing the hell out of me. > >ISS orbit numbers? You mean numbers like 13000 (ISS has made >around that many orbits)? No, what I meant was, where the "Real Time Data Orbital Elements - Shuttle" page had been referencing headings such as "Coasting Arc #11 (begining on orbit 152)," it suddenly began showing the orbit numbers as 2367, 2454, etc., which I eventually confirmed were the corresponding ISS orbit numbers. It was a curve ball I wasn't expecting. But as I said, NASA was back using shuttle orbit numbers the next day. Well, that's it. This note's gone on long enough. Jim Cook Germantown, MD 39.2N, 77.3W ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
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