REVOSAT

suivi des satellites artificiels

07 novembre 2007

ABOUT MOLNIYA-3

about_molniya
prec_molniya
rho_theta_molniya_3

The elements of typical Molniya are 40000/500 kms/63.4°.
Such elements give a semi major axis A=(40000+500)/2+6378=26628kms
C=26628-(6378+500)=19750 kms
Excentricity=C/A=19750/26628=.7417
Period T=26628^1.5/6028.9/60 =12.0120876 hours
Nb rev/day=24/12.012=1.99798 rev/day
Perigee rotation +4*10^-4°/day
Nodes precession –1.1338°/day
Among the series Molniya-3, we found a different one N°24640  in Heavens above base with such data.
Apogee=36544 kms**Perigee=94 kms**Inclination 63.6391°.
The perigee and apogee are very low compared to that of typical Molniya. (may be a problem of propulsion during the launch).
These data induce 2.236 revolutions every day instead of 2 and a precession of –1.17°/day of the ascending node and –3*10-3 °/day of the perigee instead of ~0° habitually.
Consequences.

1)The transits can take place over FRANCE during night and because of the shift of the perigee , on a height very inferior to 36000 kms.

2)The rotation of the perigee (-12°=-11*365*3*10^-3 since the launch on 1996) induce a change of the aspect of the north ground track because the speed of rotation of the earth can balance that of Molniya at a decreasing latitude and not only at 63.6 as it was the case generally.
Because the argument of perigee decrease and so about the apogee, the height of the satellite increase with years during the zenital ascending transits(ZAT) and decrease during the zenital descending transits(ZDT) over FRANCE.
If Molniya X (by ex 15738)has an argument of perigee increasing, the height of zenital ascending transits(ZAT)decrease and height of zenital descending transits(ZDT) increase over FRANCE.

 

We will tackle the aspect of loop of the ground track near apogee on REVOSAT 2008.

Posté par revosat à 16:10 - Observation - Commentaires [1] - Permalien [#]

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