JET PROPULSION LABORATORY RA-I Preliminary Flight Performance Report and Failure Analysis Submitted by Spacecraft Data Analysis Team Introduction Edited by A. E. Dickinson February 15, 1962. This report is submitted in accordance with ICM to J. D. Burke from H. M. Schurmeier dated Feb. 1, 1962. It presents the results of the findings to date concerning all discrete spacecraft failures which actually aid occur or which at one time were believed to have occurred during the hormal mission lifetime. The emphasis has been on those performance aspect. which could affect RA-IV, with the result that very little analysis has been done of the spacecraft performance after the vidicon data period. A. General- The spacecraft performance can be divided into three aistinc. phases: launch, midcourse and terminal. The launch phase was initiated by starting the CC and S timer at two minutes before liftoff. acourse and terminal phases were initiated by real time ground commands こ Les selected to optimize the ensuing maneuver sequences under abnormal trajectory conditions. Each phase consisted of a fixed sequence of events to be executed on command from the CC and S. The only variables within these sequences were the duration of the midcourse and terminal maneuver turns, the direction or polarity of each turn, and the velocity increment to Le provided by the midcourse motor. These variables were read in to the CC and S register as sets of three stored commands from the ground prior to initiating the midcourse and terminal maneuvers. The spacecraft transmitter was switched back and forth by ground command to transmit over the low gain quasi-omnidirectional antenna or the high gain directional antenna. The spacecraft transmitter was on low gain antenna until first Goldstone acquisition and during the midcourse maneuver. It was twice commanded over during the vidicon period without noticeable effect. Other ground commands were available to compensate for non-standard performance but were not used until the vidicon period was terminated by switching the spacecraft data encoder back to engineering telemetry mode. Launch Phase The following functions are performed during the B. launch phase (A = CC and S start time): (1) Capsule transmitter turned on and squib firing assembly armed by inertial switches during the boost phase. (4) Sun acquisition initiated at A + 36 min. (5) Earth acquisition initiated at A+ 213 min. (6) Gamma ray spectrometer power turned on at A+ 243 min., readou sequence starts 1 miss later. All of these events were confirmed. The exact times for items (1) and (2) cannot be determined but items (3) through (6) occurred at the programmed times. One very significant spacecraft failure occurred during this phase of the flight. At the time the squibs were fired to unfold the solar panels a sudden drop was noted in received signal level at DSIF 5. (The mobile tracking station was out of lock at the time.) The low gain antenna drive measurement preceding this event indicated about 35 dbm, the normal value after the transmitter power is increased. The next sample after the event showed this measurement had dropped to about 23 dbm, where it remained until the transmitter was switched to the high gain antenna. The RF drive level also showed a slight decrease at the time the antenna drive decreased. A second malfunction during this phase occurred in the gamma ray spectrometer. The detector temperature started rising abnormally right after it was turned on and the instrument gain increased. During the operation other malfunctions were believed to have occurred, but subsequent examination of telemetry analog records showed these to be the result of faulty digital sampling and a bad filter in the Channel 4 discriminators. (Note: The DRL is still having Channel 4 discriminator problems under weak signal conditions with the result that much of data from this channel has had to be reduced by hand.) C. Midcourse Phase Recovery of spacecraft telemetry during the latter part of the midcourse maneuver pitch turn, the motor firing and start of sun reacquisition was seriously hindered because the spacecraft was commanded to an orientation that violated the omniantenna constraint. This was a calculated risk decided upon during the operation and was complicated by the following factors: (1) the spacecraft turned in the opposite direction from that predicted; (2) the transmitted signal from the low-gain antenna was abnormally low; (3) the receiver at DSIF 2, the more sensitive of the two Goldstone receivers, apparently had a malfunction during this period. The problem of the spacecraft command polarities was covered in J. F. McGee's IOM to H. M. Schurmeier dated 2/5/62. Regardless of direction, the commanded 116° pitch turn would have placed the look angle (or the earthprobe line) within one of the omniantenna null cones about the spacecraft roll axis. 32-445 O - 64 - 30 Sufficient telemetry has been recovered to indicate that the CC and S program for the midcourse phase was apparently normal. The events in this sequence are listed in Table IV-1 in Part IV of this report. No motor firing data has been recovered except cutoff blips, but the system apparently functioned normally. The gamma ray spectrometer temperature apparently continued to rise until the boom was extended when it started to cool off. The gain, however, increased again following extension. An abnormal functioning of the Deck G temperature bridge was noted following the midcourse maneuver. D. Terminal Phase- The programmed sequence of terminal maneuver events is listed in Table IV-2 in Part IV. The CC and S failure which occurred during that period is also discussed in Part IV. No engineering data is telemetered except event blips after the last pitch turn is completed, because the same CC and S command which stops the turn also switches telemetry modes and nothing but science data is transmitted. The commands to the squib firing assembly for uncovering vidicon lens and deploying the altimeter and omniantenna were apparently normal. The commutation of science data and the altimeter turn on showed no irregularities. In addition to the extraneous pitch command the following malfunctions were noted in the terminal sequence: an extraneous gamma ray readout at the time of the maneuver execute command RTC-6; no confirmation of the altimeter extension; possibly abnormal temperature in the vidicon camera. |