tableau__precession

These two satellites are heliosynchronous and the time of their trajectory zenithal ascending transit ZAT are at present quasi the same.22H45(2).So regularly they transit together see photo with Metop-A flaring and USA 129 mag4.4 on 20 april 07 22H12 (2).

USA 129, satellite very eccentric, (277*996kms*97.8°) having a perigee of 277kms shifting –3.26°/day can flare too when it is on perigee ie every 360/3.26=110 days.

The Shift of Perigee is calculated by the formula:
SP=-1.189*10^7*(1-5*cos(incl)^2)*24/per/A^2/(1-EX^2)^2.

Incl is inclination of orbit=97.8°

Per is the period of revolution 1.6240 hour

A is the semi-major axis.(996+277)/2+6378=7014.5kms so mean height=636.5kms.
EX is eccentricity
Observe that SP is null if incl is~64 degrees (Satellite Molniya).

or by difference of argument of perigee 12 may 07->73.78° minus 19 may 07 ->50.96° divided by seven days (Epoch published by Heavens above) . So when could we observe these two satellites transiting and flaring together? Their period are 1.6899h Metop-A and 1.6240h USA 129 at present.

Auffargis is 48.7° latitude. So the argument of the perigee of USA129 has to be Arsin(sin(48.7*3.14/180)/sin(97.8*3.14/180))*180/3.14=49.3°

With the values published by Heavens above, the perigee has been over Auffargis on 20 th of May.110 days later ie 7th of September 2007 it will be possible to see USA129 again with a major brightness.

USA 129 is a military reconnaissance one so its elements can change. The dance between these two satellites is to be observed. On the photo, USA129 is between Apogee and perigee~650kms.

Idem for Envisat and Resurs 1-4 roc ,their ZAT being 23H15(2).

See scheme hereafter ZAT versus time in half year unit.

METOP-A FLARING AND KEYHOLE USA 129

Partager cet article