1) because the radial gradient of [phi] falls as 1/[r.sup.2], and hence most of [DELTA]v accumulates when the spacecraft is near the periapsis
whereas contribution from the long opposite inbound and outbound legs is negligible.
(a) [psi]: the angle of approach, that is, the angle between the line of the periapsis
of the trajectory of the spacecraft around the Earth and the line that connects the Sun and the Earth;
The primer vector in the direction of maximizing the argument of periapsis
Satellite comparison Satellite United States China Characteristics USA-193 Feng Yun-1C Satellite Type Reconnaissance Meteorological Satellite Mass 2,450 kg 880 kg Satellite Apoapsis 257 km 865 km Satellite Periapsis
242 km 845 km Satellite Inclination 58.48 degrees 98.8 degrees Source: "FY/1;" Encyclopedia Astronoutica, http://www/astronautix/ com/craft/fy1/htm (accessed 11 November 2008); and David A.
Therefore the Sun seems to move faster than average at periapsis
, which is currently around 3 January, and slower than average at apoapsis, which is around 4 July.
In April the spacecraft dipped its low point (periapsis
) into the Martian atmosphere, only 105 km above the surface.
where n is the mean motion of the target vehicle; m is the mass of the chase vehicle; e is the eccentricity of the target orbit; M = n(t - [t.sub.p]) is the mean anomaly of the target vehicle; and [t.sub.p] is the time of periapsis
The program includes options to display a grid, zoom in and out, change the three-dimensional perspective, and indicate details about each orbit, including the location of periapsis
and apoapsis, planet-rotation direction, and lines of nodes.
It can be seen that the thruster is on duty across the periapsis
; the only maneuver performed at the apoapsis injects the spacecraft into a nearly circular orbit to acquire the final orbit.