Exploring the Unknown: Selected Documents in ... - The Black Vault

Exploring the Unknown 355
The total distance encompassed during the braking maneuver was 0.24
nautical miles (from 0.48 to 0.24 n. mi. from the target). When the range was 0.20
nautical miles, the pilot called the range to space craft 7 in feet to the ground and
to the command pilot.
At a range of approximately 700 feet, the sunlight illuminated spacecraft
7 and the target was so bright that no stars were visible. The total impact of
the brightness was as if a carbon arc lamp had been turned on immediately in
front of spacecraft 6. The range decreased nominally, during which time both
the pilot and command pilot contin ually commented on the brightness of the
target. Because of the bright ness, the radar display and the flight director attitude
indicator (FDAI) were then used for tracking. As spacecraft 6 approached a range
of 300 feet from spacecraft 7, the pitch angle decreased to 90° and held that value.
Spacecraft 6 then continued to approach from directly be low spacecraft 7.
At 240 feet, all rates in translation, except the closing velocity, had been
reduced to zero. The closing velocity was being reduced by a series of small thrusts
to approximately 2 ft /sec. Finally, at a range of 120 feet, all relative motion
between the two spacecraft was stopped at approximately 36 minutes after the
translation maneuver.
The final braking maneuver was difficult because of (1) the bright ness
of the reflected sunlight from the target at a range of approxi mately 700 feet,
and (2) the fact that the crew could no longer use stars as a reference. Also, the
target spacecraft was changing pitch attitude in order to track spacecraft 6 and,
as a visible object, could [7-25] not be used for attitude reference with relation to
motion in a pitch maneuver of spacecraft 6.
A very low, relative translation rate remained near the end of the braking
maneuver. Spacecraft 6 had moved from a pitch angle of 90° to a pitch angle of
60° by the time the forward relative velocity was re duced to zero. The crew elected
to continue this motion at a 120-foot radius, pitching down to the SEF attitude,
and holding this position. At this point, spacecraft 6 was in the SEF position, with
spacecraft 7 facing it in BEF, and all relative motion was stopped. The attitude
control system was placed in SEF platform control mode, and all maneu vers were
then performed with the maneuver controller.
The performance of the guidance and control system and radar sys tem
during all phases of rendezvous was excellent and the use of radar for rendezvous
was shown to be extremely valuable. Throughout the ren dezvous phase, the radar
maintained positive lock-on and an accurate indication of range was available
through the minimum readable value of 60 feet. The attitude indications were
steady throughout the entire maneuver.
7.1.2.4 Station keeping.- From the crew’s analysis of the timing, spacecraft
6 arrived in formation with spacecraft 7 about 23 seconds earlier than predicted
prior to lift-off. In the SEF attitude, the distance between the spacecraft was
closed to approximately 6 to 10 feet in order to observe spacecraft 7 in detail.
Still photographs and mo tion pictures were taken and all exposure values were
determined with the spot meter. The results of this photography indicate that a