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Aviation History
1967
1967 - 0188.PDF
182 FLIGHT International, 2 February 1947 Spaceflight equipment resumed normal operation except for a loss of a row (20 channels) of spacecraft status data. "Contact with the observatory from the Rosman ground station during the first orbit indicated that several other anom- alies had occurred subsequent to the Australia contact: the spacecraft clock had been reset unexpectedly; the spacecraft was in roll-search; two more rows of status data had been lost and the temperature of the battery being used had risen slightly. "Such anomalies persisted throughout the short life of the spacecraft. The periodic unintentional resetting of the space- craft clock, about every other orbit, prevented effective pro- grammed control of the spacecraft when it had passed out of real time control. The loss of status data channels further handicapped spacecraft analysis. "In order to reduce the battery temperature, the spacecraft was placed into a temporary tumble mode in orbit No 17 in order to induce battery cooling through reduced charging. How- ever, this resulted in battery depletion and after orbit No 20, on April 10, 1966 no further communications were received. The experiments were never activated. . . ." The probable "direct and immediate cause" of the OAO-1 failure was traced to a failure in the battery charge and sequence controller, which appeared to have caused over- charging of a battery pack and the power system. It was further believed that the major disruption of the operation of the spacecraft was caused by arcing in the star-trackers. Although it could not be proved conclusively that star-tracker arcing did occur in orbit, ground tests showed that many of the observed operating anomalies could be duplicated when the star-trackers were caused to arc. It was not possible to determine whether failure of the battery charge and sequence controller was associated directly with star-tracker arcing, because telemetry during launch was not available and half of the in-flight spacecraft analogue data was lost—apparently because of the arcing. Other weaknesses in the spacecraft system were identified which could have contributed towards the OAO failure. These included "noise susceptibility of the stabilisation and control subsystem and the communication and data-handling sub- system that resulted in initiation of restabilisation, jet firing, star-tracker mode switching, error bursting, and loss of data channels, tracking of false stars by the star-trackers; operation problems with the unloading of the momentum wheels and execution of stored commands; and possible thermal prob- lems in the battery compartment." The review board recommended that the OAO spacecraft subsystems should be modified to include the following im- provements : — (1) Provisions for the reliable charging and control of the batteries including redundancy (parallel operation); a power system not dependent on spacecraft manoeuvring to achieve a negative energy balance (deep discharge of batteries); and separate spacecraft-ground complex battery connections for battery conditioning. (2) Elimination of arcing, error bursting, and false star- tracking, suppression of noise generation; and reduction of noise sensitivity in all equipments. (3) Provision for stabilisation and control with the ability to hold the attitude of the spacecraft by an inertial system (such as an improved version of the rate and position system currently planned for the next mission) during star occultation and other desired holding modes; circuit logic to permit a reliable determination of when the control system can switch to the fine pointing mode; and means for unloading the fine momentum wheels when not in fine pointing. (4) Provisions for spacecraft status telemetry from count- down, through launch and orbital phases; adequate telemetry with proper time identification encoded into the data. (5) Changes in interfaces to protect the equipment from electromagnetic interference and other potential sources of failure. In addition to these design changes required by technical aspects of the OAO-1 failure, the board recommend a number of other improvements. These were based on a general up. dating in the fields of mission analysis, system and subsystems analysis, systems testing, flight operations and project support In particular the board recommended that the testing pro. gramme should be extended to simulate more fully the expected space environment, and should readopt the use of a prototype model for each of the OAO missions. The OAO project organisation at Goddard Space Flight Centre should be strengthened. In addition to the ad hoc investigation of the OAO-1 failure, the. review board completed a general investigation of project practices in all NASA's observatory-class spacecraft—the Orbiting Geophysical Observatory and Orbiting Solar Observa- tory series as well as the OAO satellites. AH these programmes were handled by J3.oddard Space Flight Centre, whose record since 1959 comprised a total of 50 spacecraft successfully injected into orbit. Of these, 42 were non-observatory types (41 of which were successful), while the observatory spacecraft had comprised five successes and three failures. The successes were OSO-1, OSO-2, Nimbus 1, Nimbus 2 and OGO-3, and the failures were OGO-1, OSO-2 and OAO-1. The board commented that the observatory-class spacecraft were generally larger and more complex than Goddard's other satellites; their development contracts had been initiated be- tween September 1959 and June 1961; the record of observa- tory spacecraft performance had been achieved without the benefit of engineering test flights; and OGO-1 and 2, recorded as failures because they did not achieve stabilisation, had in fact accomplished more than half of their scientific objectives in a spinning mode—and had collected more scientific than all other Goddard geophysical satellites combined. As in the OAO-1 investigation, the board concluded that many improvements were needed stemming from the early date at which the various observatory satellites had been con- ceived. They did not reflect the current state of the art in a number of areas. The board recommended a number of specific improvements in management, design, reliability and quality assurance methods, test procedures and spaceflight operations and direction at the Goddard centre. LUNA 12 COMPLETES PROGRAMME The Soviet news agency Tass reported on January 21 that Luna 12, the third Soviet lunar satellite, had successfully completed its flight programme. It was placed in orbit around the Moon on October 25. The Tass report continued: — "When the station was in its 602nd orbit of the Moon on January 19, radio communication with the station was ended. Luna 12 has covered 9,800,000km around the Moon, and 302 radio-communication sessions were held with it. During its three-month flight Luna 12 carried out a great amount of scientific research and transmitted back to Earth pictures of the lunar surface. "Detailed measurements of the gamma radiation by the lunar surface, X-ray fluorescent radiation, corpuscular radiation and the density of the micro-meteoric matter near the Moon were carried out. Radio-astronomical observations in the long-1 wave range, begun by Luna 11, were continued." Explorer 1 Still There Explorer 1, the first satellite launched 1 into orbit by the USA (on January 31, 1958), is still in orbit after nine years. Present orbit is at 210-890 miles, and the expected date of decay is late 1969. Diamant Satellites Two more French scientific satellites, designated D-1C and D-1D, are scheduled to be launched the third and fourth Diamant vehicles from Hammaguir dur- ing this month. These will be the last satellite launching* from the Sahara site. Cosmos 139 was launched into Earth orbit at 144-210km, 50' inclination, on January 25, but apparently was recovered fr0111 orbit within 24 hours. The satellite apparently was launched! from the site near Archangel and may be associated with the 1 recent unannounced spacecraft known as Cosmos U-l and U-l both of which exploded or separated into a large number , pieces.
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