In a message dated Thu, 14 Sep 2000 09:39:35 -0400 "Kevin Fetter" <kfetter@yahoo.com> writes: >If I am not mistaken about reading the data on the below site then > >A good site to find out when the ISS space shuttle and mir are going to >have orbit changes using their engines is at >http://spaceflight.nasa.gov/realdata/elements/ Kevin is correct. When today's predicted TLEs showed a rather dramatic shift in the predictions I was coming up with, I suspected yet a THIRD reboost was sheduled. What I didn't know was that there is in fact at fourth reboost scheduled as well. I wrote Jonathan Weaver, the person who oversees the Real Time Data pages, and this is what I was told: In a message dated 9/14/0 1:02:57 PM, jonathan.k.weaver1@jsc.nasa.gov writes: >Yes, yesterday they decided to add another ISS orbit raise maneuver >( origionally there were only going to be three, now 4 ). >Thus they executed the second one around 258:6:15:47 UTC. Both the >Shuttle and Iss orbital elements files begin at UTC time around >258:9:45:00. Thus they reflect this burn and the remaining two upcoming >burns are in the maneuver table and are reflected in the Vehicles >appropriate coasting arcs. > >When you are generating sightings in the future, and there are maneuvers >in the timeline, be sure that you are using a coasting arc TLE that is >reflecting the actual trajectory profile for your timeframe of interest! >If you continue to coast a TLE and another maneuver occurs, but you dont >re-initialize with the next coasting arc TLE, then large timing errors >may occur. > >We try to keep the web site updated in a timely fashion but mission >priorities sometimes arise, and realtime decisions to change the >trajectory profile can happen ( as shown yesterday when they decided >to add another orbit raise maneuver). > .>.. when we re-fresh the data on the web you will need to re-run your >sightings predictions for passes that havent yet occured to be sure >that the previous computed times are still valid! I'm hoping they will be updating their ISS TLEs as well -- the last time I checked (earlier this morning) it still showed the TLE's that were predicted as of yesterday, apparently not reflecting these additional reboosts. So with undocking scheduled so close to Monday morning's passes, they have to be closer together than the five minutes I'm coming up with now, using yesterday's ISS TLEs. 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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