When writing about the node, I was actually referring to the geocentric LAN, not the inertial RAAN. I should have specified. The phasing and the LAN are interconnected, as you know. The LAN (along with the overall groundtrack, as Sean described) has been shifted to the west to bring Edwards into the Shuttle's entry crossrange capability on the desired orbit. Tom The opinions expressed are my own and not those of NASA. -----Original Message----- From: Aaron Brown [mailto:asb110273@gmail.com] Sent: Thursday, June 21, 2007 8:13 PM To: seesat-l@satobs.org Subject: Re: Verify your Atlantis predictions. It seems that increasing the semi-major axis would reduce the negative drift of the RAAN, putting the RAAN further east than it otherwise would be. This would seem to have the opposite effect as desired. As Sean mentions, I think it has more to do with the phasing of the orbit. We don't really need the earth to turn for another 90 minutes to get the de-orbit opportunity. Instead of waiting one extra full orbit to deorbit to EDW, we slow down the orbit rate just enough to allow the earth to turn under us just enough. See Sean's email for a good explanation of this. Aaron -----Original Message----- From: Sean Sullivan [mailto:seesat@golux.org] Sent: Thursday, June 21, 2007 5:54 PM To: SeeSat-L@satobs.org Subject: Atlantis orbital adjustment This is just some casual speculation building on what I read in Bill Harwood's article, and I haven't looked at the elements or thought this through carefully. But since there were a lot of messages about how this adjustment might affect the position of the shuttle, I thought I'd try giving an intuitive explanation. It sounds like NASA wants to create a landing opportunity at Edwards one orbit before Atlantis would have (on its original orbit) had a shot there. On this orbit, therefore, the Atlantis groundtrack would have been too far east, and NASA wants to nudge the groundtrack west. Since the earth is turning west-to-east under the orbit, this is accomplished by giving the earth more time to rotate before the shuttle crosses a given latitude. To do this, the shuttle needs to run late relative to its original timing. Thus, the orbital period needs to be increased, and that's done by raising the orbit. So I would expect to see Atlantis fall behind relative to its original trajectory. Also, here's a wide-angle photo of Atlantis and ISS last night from Boston, in a 10-second exposure: http://photo.ztn.net/static/satellites/sts117.jpg Sean Sullivan On 6/21/07, Erkenswick, Tom M. (JSC-DM3) <tom.m.erkenswick@nasa.gov> wrote: > > Chris, > > That is not what was meant by "earlier opportunity." The purpose of the burn is to change the orbit's major axis, thus affecting the orbit's nodal regression, which brings Edwards into the crossrange limits one rev earlier than with the current orbit - in other words, it "buys" us an extra deorbit opportunity on an earlier rev, and based on the quote below it sounds like they're trying to land prior to the forecasted wind increase. I believe the burn is posigrade, which means Atlantis will be later than current elements. > > Tom > > > The opinions expressed are my own and not those of NASA. > > > > -----Original Message----- > From: Chris Jones [mailto:clj@panix.com] > Sent: Thursday, June 21, 2007 2:39 PM > To: seesat-l@satobs.org; brad.young@domain-engineering.com > Subject: Re: Verify your Atlantis predictions. > > Brad Young wrote: > > Pardon my orbital ignorance, but wouldn't a scrub mean they would just > > continue their present orbit, slowly falling further behind ISS (since still > > higher) until de-orbit burn less than an hour before landing? So, > > practically speaking, look for ISS and wait, similar path a few minutes > > later? > > This is an excerpt from the "CBS Space News" mailing list sent out by William > Harwood: > > astronaut Dominic "Tony" Antonelli radioed [Atlantis]... "At Edwards, the > winds are going to pick up. So what we've come up with is in about three > hours, we're going to do an 11-foot-per second (rocket firing) and what > that's going to do for us is pull in an earlier Edwards opportunity" > > so it would seem that, after the rocket firing, Atlantis will be arriving > along its orbit earlier than the current elements would predict. > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > > ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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