ATLAS AGENA PAYLOAD SOFTWARE

After the Agena was released, it coasted for 50 seconds and then fired its thrusters for ullage to settle the propellants in their tanks prior to firing the main engine for orbital insertion. The first of these vehicles lifted off from Pad 14 at Canaveral on 25 October 1965. This Gemini-Agena Target Vehicle also had a pair of thrusters mounted in 'saddle bag' fashion on each side of the main engine. In addition, in June 1962 NASA ordered a variant of the Agena on which theĪtlas models (left to right): Atlas-D, 20 February 1962 with John Glenn in a Mercury capsule Atlas-Able, 26 November 1959 with Pioneer P3 (lost when the shroud collapsed after 45 seconds) Atlas-Agena-A, 26 February 1960 with MIDAS 1 Atlas-Agena-B, 9 September 1961 with SAMOS 3 Atlas-Agena-D, 30 September 1965 with the 22nd KH-7 satellite.Įngine could be fired as many as six times to enable it to undertake orbital manoeuvres while docked to a manned Gemini spacecraft. The other incident was on 4 December 1971, when an Atlas was lost with a Canyon communications intelligence-gathering payload. However, it was able to be revised in time to dispatch Mariner 4 on 28 November, a few days before the 'window' for a mission to Mars closed, and the pictures that it snapped during a 10,000-kilometre flyby on 15 July 1965 revealed the surface of the planet to be scarred by large impact craters.

An investigation found that the new lightweight shroud had bonded to the probe. On 5 November 1964 Mariner 3 was trapped when the shroud failed to separate. The Atlas-Agena-D had the MA-5 power plant.17*18 Of 27 launches between 12 July 1963 and 7 April 1978 there were only two failures.

There were another two successes, then MIDAS 6 was lost on 17 December 1962 and MIDAS 8 on 12 June 1963. Mariner 2 was successfully dispatched on 27 August and became the first spacecraft to return data about another planet when it flew past Venus on 14 December 1962 at a range of 35,000 kilometres. It was found that the hyphen had always been missing, but had been benign since there had been no radio guidance failure on the previous flights. Due to an oversight, a hyphen had been omitted from the program, and this had the effect of allowing the flawed signals to command the vehicle to veer left and drop its nose. However, at this point a second fault took effect.

In the event that radio guidance was lost, the autopilot was supposed to reject the spurious signals from the antenna and proceed on its stored program. When the received signal became weak and noisy, the vehicle lost its lock on the ground reference that supplied steering commands.

ATLAS AGENA PAYLOAD SOFTWARE

Although this is often cited as the exemplar of the loss of a mission to a software error, in fact, as is often the case, two independent faults had interacted fatally.16 The guidance antenna on the Atlas performed below specifications. After a string of successes, Mariner 1 was lost on 22 July when the Atlas flew off course and at T + 293 seconds was destroyed by the range safety officer. With Ranger 3 was able to restart to leave parking orbit, but a guidance fault made the probe miss the Moon by some by 37,000 kilometres. After SAMOS 4 was lost on 22 November, SAMOS 5 was successfully placed into orbit on 22 December but failed to return its film capsule.

MIDAS 4 was successfully dispatched on 21 October, but on 18 November Ranger 2 was stranded in parking orbit when an inoperative roll gyroscope prevented the Agena restarting. The next launch on 9 September with SAMOS 3 was a total loss when the vehicle exploded on the pad. On 23 August 1961, on the second mission, the Agena attained low 'parking orbit' and then failed to restart to make the burn that was to insert the Ranger 1 spacecraft into a highly elliptical orbit. The Atlas-Agena-B had the MA-3 power plant.15 Of 28 launches between 12 July 1961 and 21 March 1965, eight suffered problems. On 11 October the Agena with the first of the Satellite and Missile Observation System (SAMOS) satellites failed, but the second was launched on 31 January 1961. On the first launch, on 26 February 1960, the Agena with the first satellite for the Missile Defense Alarm System (MIDAS) failed to separate from its booster, but the second was inserted into orbit on 24 May. The Atlas-Agena-A employed the MA-2 power plant.14 Two of four launches failed. As the Agena was stretched to carry more propellant, and its engine was made both more powerful and capable of being restarted in space, it became available in A, B and D models (the planned C model was cancelled). The decommissioned Atlas-D missiles were fitted with Agena upper stages for use as space launchers.

Atlas agena payload