**Previous message:**George Roberts: "Re: Low orbit objects list?"**In reply to:**Darwin Teague: "Low orbit objects list?"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Back on about the 16th March I posted some questions about calculating this from the two line elements - here is how to calculate it yourself. You'll need 3 values: e = eccentricity from the TLE n = radians per second (mean motion in the TLE is in orbits per day and needs conversion) GM = Geocentric Gravitationsl Constant If we take the space station as an example, (figures from a few weeks ago) show the eccentricity as 0.0009604 and the mean motion as 15.71470012 n = 0.00114280524 (meanmotion * pi * 2 / secondsinaday) GM = 398600.4418 SemimajorAxis = cuberoot(GM / n ^ 2) = 6732.8 kilometres This is from the centre of the earth. For eccentricities of 0 (circular orbits) it is also the Semi Minor Axis, otherwise you can calculate the Semi Minor Axis with the formula found at http://en.wikipedia.org/wiki/Eccentricity_(mathematics)#Ellipses Depending on how accurate you want to be, there are many different ways to calculate the radius of the earth, or simply use 6378.1 km as a fairly good average. Note: I'm using the caret (^) as an exponent function. n^2 = n * n John On 31 Mar 2009, at 15:37, Darwin Teague wrote: > I am trying to find objects in orbits below 400 km. I take photos of > the ISS and could use practice tracking fast moving objects. The > only place I have found to see the perigee and apogee figures is in > my favorites page on Space-Track. > So far I have these: > > TITAN 3C TRANSTAGE DEB > 1 01882U > > ROSAT > 1 20638U > > TRMM > 1 25063U > > ISS (ZARYA) > 1 25544U > > PROGRESS-M 65 > 1 33340U > > ISS DEB (TOOL BAG) > 1 33442U > > OMID > 1 33506U > > Is there a way for me to find more? > > Thanks. > > > My web pages > http://negligentdischarge.com > http://loadmastervideos.com > http://darwinsastroworld.com/ > > ------------------------------------------------------------------------- > 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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