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

Exploring the Unknown 353
therefore, lock- on was continuous during the alignment period. The radar was
nulled on [7-22] the target, and the target lights appeared very dim in the sight at
this time. The target lighting was evaluated as sufficient for subsequent tracking
and angular measurements.
At this time, an estimation was made, using the data entered on the targetcentered
coordinate plot, that the first midcourse correc tion would require slight
forward and up velocities. The IVI’s indi cated 7 ft/sec forward, 7 ft/sec up, and 5
ft/sec left at a p.e.t. of 11 minutes 40 seconds. This p.e.t. corresponds to 5:31:31
g.e.t. After the midcourse correction thrust was applied, the IVI read zero in all
axes. A second tight tracking of the target was required again between 15 minutes
and 17 minutes p.e.t. It was not difficult to ob serve the docking light on the target
spacecraft at this time. The acquisition lights did not show clearly, but they could
have been tracked for backup solutions from approximately 12 minutes after the
transfer maneuver through final rendezvous.
During the second period of tight tracking, the range rate was noted
from the analog meter at 15 minutes 30 seconds p.e.t. and indi cated 90 ft/sec.
The computer data gave a range rate at this time of 91 ft/sec. At 16 minutes
30 seconds p.e.t., the analog meter indicated a range rate of 85 ft/sec and the
onboard computed range rate was also 85 ft/sec. At 17 minutes p.e.t. the range
to the target was 7.7 nautical miles. After this data point was obtained, the desired
velocity changes in guidance axes were zeroed in the computer, and tight track ing
was maintained for a period of 3 minutes to determine the backup solution for
a normal-to-the-line-of-sight correction. The command pi lot remarked that the
spacecraft 7 docking light was as bright as the Agena. At 16 minutes p.e.t. (5:35:51
g.e.t.) the pilot remarked that he could see the docking light even though he had
a brightly lighted area in the cockpit.
The docking light on spacecraft 7 was displaced 0.50 to the right of the zero
position in the optical sight, while using the radar null as the pointing command.
Farther to the left, approximately 100, two bright stars, Castor and Pollux, were in
sight. These stars provided excellent pitch, roll, and yaw reference. In addition,
there were suf ficient stars near and around the target to permit good tracking. It
was also noted that the docking light obscured the acquisition lights because of
its relatively greater brilliance. However, the spacecraft 6 crew requested that the
spacecraft 7 docking light be left on.
The target-centered coordinate plot indicated that small up and forward
corrections would be required for the second mid-course correc tion. The backup
solution indicated 6 ft/sec up. No backup velocity correction along the line of
sight could be obtained because the computer math flow locked out ranges at
this time. At 23 minutes 40 seconds p.e.t., the computer solution gave a correction
of 4 ft/sec forward, 3 ft/sec up, [7-23] and 6 ft/sec right. When this maneuver
was completed, the IVI was zeroed and the computer switched to the catchup
mode. The pilot then cleared MDRU addresses 25,26, and 27 (X, Y, and Z, desired
velocity changes in guidance axes) and the IVI displayed all zeros.
From this point, the pilot continually called out the pitch angle to
spacecraft 7 as it increased and the range decreased. The command pilot, at this