Ranger 6 was designed to achieve a lunar impact trajectory and
to transmit high-resolution photographs of the lunar surface
during the final minutes of flight up to impact. The spacecraft carried six television vidicon cameras, 2 full-scan cameras (channel F, one wide-angle, one narrow-angle) and 4 partial scan cameras (channel P, two wide-angle, two narrow-angle) to accomplish these objectives. The cameras were arranged in two
separate chains, or channels, each self-contained with separate
power supplies, timers, and transmitters so as to afford the
greatest reliability and probability of obtaining high-quality
video pictures. No other experiments were carried on the
spacecraft. Due to a failure of the camera system no images
were returned.
Spacecraft and Subsystems
Rangers 6, 7, 8, and 9 were the so-called Block 3 versions of
the Ranger spacecraft. The spacecraft consisted of a hexagonal
aluminum frame base 1.5 m across on which was mounted the
propulsion and power units, topped by a truncated conical
tower which held the TV cameras. Two solar panel wings, each 73.9 cm wide by 153.7 cm long, extended from opposite
edges of the base with a full span of 4.6 m, and a pointable
high gain dish antenna was hinge mounted at one of the corners
of the base away from the solar panels. A cylindrical
quasiomnidirectional antenna was seated on top of the conical tower. The overall height of the spacecraft was 3.6 m.
Propulsion for the mid-course trajectory correction was
provided by a 224-N thrust monopropellant hydrazine engine
with 4 jet-vane vector control. Orientation and attitude control
about 3 axes was enabled by 12 nitrogen gas jets coupled to a
system of 3 gyros, 4 primary Sun sensors, 2 secondary Sun sensors, and an Earth sensor. Power was supplied by 9792 Si
solar cells contained in the two solar panels, giving a total
array area of 2.3 square meters and producing 200 W. Two
1200 Watt-hr AgZnO batteries rated at 26.5 V with a capacity
for 9 hours of operation provided power to each of the separate communication/TV camera chains. Two 1000 Watt-hr
AgZnO batteries stored power for spacecraft operations.
Communications were through the quasiomnidirectional
low-gain antenna and the parabolic high-gain antenna.
Transmitters aboard the spacecraft included a 60 W TV
channel F at 959.52 MHz, a 60 W TV channel P at 960.05
MHz, and a 3 W transponder channel 8 at 960.58 MHz. The
telecommunications equipment converted the composite video
signal from the camera transmitters into an RF signal for
subsequent transmission through the spacecraft high-gain
antenna. Sufficient video bandwidth was provided to allow for
rapid framing sequences of both narrow- and wide-angle
television pictures.
Mission Profile
Ranger 6 was launched into an Earth parking orbit and injected
on a lunar trajectory by a second Agena burn. The midcourse
trajectory correction was accomplished early in the flight by
ground control. On February 2, 1964, 65.5 hours after launch,
Ranger 6 impacted the Moon on the eastern edge of Mare Tranquillitatis (Sea of Tranquility) at 9.3866 N, 21.4806 E (impact site identified from Lunar Reconnaissance Orbiter images). The orientation of the
spacecraft to the surface during descent was correct, but no
video signal was received and no camera data obtained.
A review board determined the most likely cause of failure was due to an arc-over in the TV power system when it
inadvertently turned on for 67 seconds approximately 2 minutes
after launch during the period of booster-engine separation.
Total research, development, launch, and support costs for
the Ranger series of spacecraft (Rangers 1 through 9) was
approximately $170 million.