Angular motion of the spin axis of the Tiros I meteorological satellite due to magnetic and gravitational torques

Abstract

The Tiros I meteorological satellite was injected into orbit about the earth on April 1, 1960, at 11h 52m GMT. The purpose of the satellite was to photograph cloud patterns and distribution over the earth [Stroud, 1960].In order to properly command the satellite from the ground to take direct or remote pictures, and in order to analyze these pictures when they are telemetered to the ground, the time, spatial coordinates, and spin-axis attitude of the satellite must be known. Ephemerides based on tracking data from the worldwide Minitrack Station Network and published by the NASA Space Computing Center determine accurately the spatial coordinates as a function of time. It was thought that, except for small perturbations, the spin-axis attitude would be space-stabilized for the nominal 3-month life of the satellite.

Satellites and meteorology

“…Практически оказалось, что направление оси вра-щения спутника не остается постоянным ввиду возмущений, вызван-ных влиянием магнитного и гравитационного полей Земли (см. 9 ). Од-нако на спутнике был преду-"/ ^ ,----•…”

High-accuracy attitude control of satellites in elliptic orbits

“…The orbits of the satellites are elliptic, although for satellites (2) and (3) the eccentricity is assumed to be only 0 01. The orbits are not considered circular since suon an assumption is generally a gross oversimplification and since the number of orbits a satellite will complete before the aerodynamic forces cause it to move on a trajectory back to earth increases with eccentricity (Breakwell and Koehler [4] have derived an expression for the number of oroits before decay This expression, which gives a lifetime of about 10,000 orbits (about 1 7 years)…”

“…Consider the "stable" satellite (2) Busch -suggests a reaction wheel moment of inertia of I -l0 5 ) I = 1.21 slugs-ft. 2 . If the reaction wheel is a brass cylinder with a diameter of 1.5 ft. and a height of one foot, the weight of the reaction wheel as 138 lbs.…”

“…• 59 4 4 Nearly Minimum Fuel Boundary Encounter Trajectories for 5.4 Suboptnmally Controlled Acquisition Motion of Satellite (2), J = a Roll-Yaw of Satellites (2) and ( Figure 4 17- At this time there are many planned artifical earth satellites which must perform tasks which reqaire a given satellite-fixed line to be (nearly) parallel to the local vertical while the angles between every satellite-fixed line and tne orbit plane are (nearly) constant. This required orientation is called (near) earth-pointing Earth-pointing is not a natural satellite orientation so that control effort must be spent to keep the orientation (celled station-keeping) once it has been acquired.…”

“…system ) The overall control system which is very simple to realize, is given in diagram form (4 3)-(4 6) for Satellite (2) . • 59 4 4 Nearly Minimum Fuel Boundary Encounter Trajectories for 5.4 Suboptnmally Controlled Acquisition Motion of Satellite (2), J = a Roll-Yaw of Satellites (2) and ( Figure 4 17- At this time there are many planned artifical earth satellites which must perform tasks which reqaire a given satellite-fixed line to be (nearly) parallel to the local vertical while the angles between every satellite-fixed line and tne orbit plane are (nearly) constant.…”