Results: The mission of Able VB, like its two unsuccessful predecessors, was to enter lunar orbit. Scientific objectives included studying radiation near the Moon, recording the incidence of micrometeoroids, and detecting a lunar magnetic field. Planned lunar orbital parameters, to be achieved about 60 hours after launch, were 4,300 × 2,400 kilometers with a period of 9–10 hours. The spacecraft had a slightly different scientific instrument complement than its predecessors, including a plasma probe experiment designed by NASA's Ames Research Center that was to provide data on the energy and momentum distribution of streams of protons with energies above a few kilovolts per particle in the vicinity of the Moon. Unfortunately, the Atlas Able booster suffered a malfunction 66.68 seconds after launch and then exploded at T+74 seconds at an altitude of about 12.2 kilometers. Later investigation indicated that the Able upper stage prematurely ignited while the first stage was still firing. This was the third and last attempt by NASA to launch a probe to orbit the Moon in the 1959–1960 period.
21 Heavy Satellite [Venera]
- Nation: USSR (12)
- Objective(s): Venus impact
- Spacecraft: 1VA (no. 1)
- Spacecraft Mass: c. 645 kg
- Mission Design and Management: OKB-1
- Launch Vehicle: Molniya + Blok L (8K78 no. L1-7V)
- Launch Date and Time: 4 February 1961 / 01:18:04 UT
- Launch Site: NIIP-5 / Site 1/5
Scientific Instruments:
- infrared spectrometer
- ultraviolet spectrometer
- micrometeorite detectors
- 2 ion traps
- magnetometer
- cosmic ray detectors
Results: This was the first attempt to send a spacecraft to Venus. Original intentions had been to send the 1V spacecraft to descend and take pictures of the Venusian surface, but this proved to be far too ambitious a goal. Engineers instead downgraded the mission and used the 1VA spacecraft for a simple Venus atmospheric entry and impact. The 1VA was essentially a modified 1M spacecraft used for Martian exploration (albeit with a different main engine, the S5.14 with a thrust of 200 kgf). The spacecraft contained a small globe containing various souvenirs and medals commemorating the mission. It was also the first Soviet mission to use an intermediate Earth orbit to launch a spacecraft into interplanetary space. Although the booster successfully placed the probe into Earth orbit, the fourth stage (the Blok L) never fired to send the spacecraft to Venus. A subsequent investigation showed that there had been a failure in the PT-200 DC transformer that ensured power supply to the Blok L guidance system. The part had evidently not been designed for work in vacuum. The spacecraft+upper stage stack reentered on 26 February 1961. The Soviets announced the total weight of the combination as 6,483 kilograms without specifying any difference between the payload and the upper stage. In the Soviet press, the satellite was usually referred to as Tyazhelyy sputnik or "Heavy Satellite."
22 Automatic Interplanetary Station [Venera 1]
- Nation: USSR (13)
- Objective(s): Venus impact
- Spacecraft: 1VA (no. 2)
- Spacecraft Mass: 643.5 kg
- Mission Design and Management: OKB-1
- Launch Vehicle: Molniya + Blok L (8K78 no. L1-6V)
- Launch Date and Time: 12 February 1961 / 00:34:38 UT
- Launch Site: NIIP-5 / Site 1/5
Scientific Instruments:
- infrared spectrometer
- ultraviolet spectrometer
- micrometeorite detectors
- ion traps
- magnetometer
- cosmic ray detectors
Results: This was the second of two Venus impact probes that the Soviets launched in 1961. This time, the probe—which many years later was retroactively named "Venera 1"—successfully exited Earth orbit and headed towards Venus. On the way to Venus, on 12 February, data indicated unstable operation of the system designed to keep the spacecraft permanently oriented to the Sun, needed to generate energy from its solar panels. The spacecraft was programmed so that if such a problem occurred, it would automatically orient itself toward the Sun using gyroscopes, and then shut down non-essential systems. Unfortunately, it automatically shut down its communications system for five days until the next planned communications session, because it detected higher than usual temperatures in the spacecraft. The extra heat was due to the failure of mechanical thermal shutters designed to regulate heat in the vehicle. Despite these problems, the spacecraft responded properly during a communications session on 17 February 1961 at a distance of 1.9 million kilometers when scientific data on interplanetary magnetic fields, cosmic rays, and solar plasma was returned. Unfortunately, controllers were unable to regain contact during a subsequent communications attempt on 22 February. A later investigation indicated that the spacecraft had lost its "permanent" solar orientation due to an optical sensor (that was not pressurized) that malfunctioned because of excess heat after the spacecraft's thermal control system failed. The inert spacecraft eventually passed by Venus on 19–20 May 1961 at a distance of about 100,000 kilometers and entered heliocentric orbit. Data from Venera 1 helped detect plasma flow in deep space.
23 Ranger I
- Nation: USA (10)
- Objective(s): highly elliptical Earth orbit
- Spacecraft: P-32
- Spacecraft Mass: 306.18 kg
- Mission Design and Management: NASA / JPL
- Launch Vehicle: Atlas Agena B (Atlas Agena B no. 1 / Atlas D no. 111 / Agena B no. 6001)
- Launch Date and Time: 23 August 1961 / 10:04 UT
- Launch Site: Cape Canaveral / Launch Complex 12
Ranger I and II design. Credit: NASA
Scientific Instruments:
- electrostatic analyzer
- photoconductive particle detectors
- Rubidium vapor magnetometer
- triple coincidence cosmic ray telescope
- cosmic ray integrating ionization chamber
- x-ray scintillation detectors
- micrometeoroid dust particle detectors
- Lyman alpha scanning telescope
Results: Ranger I was the first in a series of standardized spacecraft designed to take photos of the lunar surface during its descent to the Moon and rough-land simple instrumented capsules on the surface. The spacecraft consisted of a tubular central body connected to a hexagonal base containing basic equipment required for control and communications. Power was provided by solar cells and a silver-zinc battery. Ranger I's specific mission was to test performance of the new technologies intended for operational Ranger missions and also to study the nature of particles and fields in interplanetary space. Its intended orbit was 60,000 × 1.1 million kilometers. Ranger I was the first American spacecraft to use a parking orbit around Earth prior to its deep space mission. In this case, the Agena B upper stage cut off almost immediately after its ignition for trans-lunar injection (instead of firing for 90 seconds). The probe remained stranded in low Earth orbit (501 × 168 kilometers) and telemetry ceased by 27 August when the main battery went dead. The spacecraft reentered Earth's atmosphere three days later. The cause of the Agena failure was traced to a malfunctioning switch which had prematurely choked the flow of red fuming nitric acid to the rocket engine.
24 Ranger II
- Nation: USA (11)
- Objective(s): highly elliptical Earth orbit
- Spacecraft: P-33
- Spacecraft Mass: 306.18 kg
- Mission Design and Management: NASA / JPL
- Launch Vehicle: Atlas Agena B (Atlas Agena B no. 2 / Atlas D no. 117 / Agena B no. 6002)
- Launch Date and Time: 18 November 1961 / 08:12 UT
- Launch Site: Cape Canaveral / Launch Complex 12
Scientific Instruments:
- electrostatic analyzer for solar plasma
- photoconductive particle detectors
- Rubidium vapor magnetometer
- triple coincidence cosmic ray telescope
- cosmic ray integrating ionization chamber
- x-ray scintillation detectors
- micrometeoroid dust particle detectors
- Lyman alpha scanning telescope
Results: Like its predecessor, Ranger II was designed to operate in a highly elliptical Earth orbit that would take it into deep space beyond the Moon. Mission planners expected that during five months of operation, they could verify both the technical design of the vehicle and conduct key scientific experiments to study the space environment over a prolonged period. Since the Block I Rangers (Ranger I and II) carried no rocket engine, they could not alter their trajectories. On this attempt, Ranger II, like its predecessor, failed to leave low Earth orbit, the Agena B stage having failed to fire. In its low orbit, Ranger II lost its solar orientation and then eventually lost power, and reentered on 19 November 1961. The most probable cause of the failure was inoperation of the roll control gyroscope on the Agena B guidance system. As a result, the stage used up all attitude control propellant for its first orbit insertion burn. At the time of the second burn, without proper attitude, the engine failed to fire.
25 Ranger III
- Nation: USA (12)
- Objective(s): lunar impact
- Spacecraft: P-34
- Spacecraft Mass: 330 kg
- Mission Design and Management: NASA / JPL
- Launch Vehicle: Atlas Agena B (Atlas Agena B no. 3 / Atlas D no. 121 / Agena B no. 6003)
- Launch Date and Time: 26 January 1962 / 20:30 UT
- Launch Site: Cape Canaveral / Launch Complex 12
Scientific Instruments:
- vidicon TV camera
- gamma-ray spectrometer
- radar altimeter
- single-axis seismometer
Results: This was the first U.S. attempt to impact a probe on the lunar surface. The Block II Ranger spacecraft carried a TV camera that used an optical telescope that would allow imaging during descent down to about 24 kilometers above the lunar surface. The main bus also carried a 42.6-kilogram instrument capsule that would separate at 21.4 kilometers altitude and then independently impact on the Moon. Protected by a balsa-wood outer casing, the capsule was designed to bounce several times on the lunar surface before coming to rest. The primary onboard instrument was a seismometer. Because of a malfunction in the Atlas guidance system (due to faulty transistors), the probe was inserted into a lunar transfer trajectory with an excessive velocity. A subsequent incorrect course change ensured that the spacecraft reached the Moon 14 hours early and missed it by 36,793 kilometers on January 28. The central computer and sequencer failed and the spacecraft returned no TV images. The probe did, however, provide scientists with the first measurements of interplanetary gamma ray flux. Ranger III eventually entered heliocentric orbit.
26 Ranger IV
- Nation: USA (13)
- Objective(s): lunar impact
- Spacecraft: P-35
- Spacecraft Mass: 331.12 kg
- Mission Design and Management: NASA / JPL
- Launch Vehicle: Atlas Agena B (Atlas Agena B no. 4 / Atlas D no. 133 / Agena B no. 6004)
- Launch Date and Time: 23 April 1962 / 20:50 UT
- Launch Site: Cape Canaveral / Launch Complex 12
Scientific Instruments:
- vidicon TV camera
- gamma-ray spectrometer
- radar altimeter
- single-axis seismometer
Results: Ranger IV was the first American spacecraft to reach another celestial body, in this case, the Moon. Like its predecessor, also a Block II spacecraft, it was designed to transmit pictures in the final 10 minutes of its descent to the Moon and rough-land on the lunar surface a balsawood capsule (about 65 centimeters in diameter) that, among other instruments, carried a seismometer. A power failure in the central computer and sequencer stopped the spacecraft's master clock, preventing the vehicle from performing any of its pre-planned operations, such as opening its solar panels. Drifting aimlessly and without any mid-course corrections, Ranger IV impacted the Moon on its far side at a velocity of about 9,600 kilometers/hour at 12:49:53 UT on 26 April 1962. Impact coordinates were 15.5° S / 229.3° E. Although the spacecraft did not achieve its primary objective, the Atlas Agena-Ranger combination performed without fault for the first time.
27 Mariner I
- Nation: USA (14)
- Objective(s): Venus flyby
- Spacecraft: P-37 / Mariner R-1
- Spacecraft Mass: 202.8 kg
- Mission Design and Management: NASA / JPL
- Launch Vehicle: Atlas Agena B (Atlas Agena B no. 5 / Atlas D no. 145 / Agena B no. 6901)
- Launch Date and Time: 22 July 1962 / 09:21:23 UT
- Launch Site: Cape Canaveral / Launch Complex 12
Scientific Instruments:
- microwave radiometer
- infrared radiometer
- fluxgate magnetometer
- cosmic dust detector
- solar plasma spectrometer
- energetic particle detectors
- ionization chamber