HGA tracking modes
HGA tracking modes
Two rotary controls set the pitch and yaw angles of the HGA. The pointing of the antenna has three settings.
| Manual | The HGA points to the angles set into pitch and yaw controls. |
|---|---|
| Track Auto | Once the HGA has acquired a signal from Earth, Track Auto causes the antenna to lock onto its direction. Even as the spacecraft rotates, the HGA will continue to be pointed at Earth until it reaches the limits of its articulation. However, it makes no effort to reacquire Earth once the planet returns to the HGA's slewing range. |
| Reacquire | This mode is specifically intended for those periods when the spacecraft's motions are repeated and predictable. The antenna will track Earth as far as it can. Then, as the spacecraft takes the antenna away from the Earth and outside the limits of its articulation, it points itself to the angles set in the pitch and yaw controls. If these angles have been properly calculated, the further rotation of the spacecraft should bring the Earth back into the antenna's beam, whereupon it will resume automatic tracking. |
(ap15fj)
This article is based on material extracted, with permission, from the [Apollo Flight Journal] by David Woods and Frank O'Brien. The NASA Apollo Flight Journal files are copyright © 1998 - 2004. W. David Woods and Frank O'Brien.(more...)