SB ALL @ AMSAT $ANS-177.01 AO-13 Kick Motor Fired OK HR AMSAT NEWS SERVICE BULLETIN 177.01 FROM WA2LQQ WARWICK, NY June 25, 1988 TO ALL RADIO AMATEURS BT AMSAT Ground controllers have successfully fired AMSAT OSCAR 13's kick motor in orbit. The result is a successful intermediate orbit one or two steps away from the final, desired AO-13 orbit. A second kick motor firing could come within a week setting the stage for general communications operations in a few weeks. After reviewing the AO-13 attitude and spin rate, DJ4ZC gave the OK for a kick motor firing last Wednesday. The firing took place at 18:57 UTC, Wednesday, June 22. The burn coincided almost exactly with apogee of orbit number 16. The IHU was loaded with a firing routine for a 50 second burn by AO-13's 400 Newton bi-propellant kick motor. Prior to the burn decision, criteria had been established to maneuver to an attitude, in Bahn coordinates, of 90 degrees longitude and -60 degrees latitude with an angular velocity (spin rate) of 30 to 40 rpm. However, looking at various considerations such as the overall schedule and visibility of the satellite over the next week, the decision was taken at about 1630 UTC to execute the burn two and one half hours later. Estimated attitude and spin rate of AO-13 at the time of motor burn were found to be within tolerance for a burn and so it was executed. According to an analysis by Phil Karn, KA9Q, the change in AO-13 velocity due to the kick motor burn was 159.6 meters per second. This value is about 14.4% higher than the 139.5 meters per second predicted from W4PUJ's figures for spacecraft mass, motor performance, and propellant flow rates. Based on the direction of the delta-velocity vector, the attitude of the spacecraft in pre-burn Bahn coordinates was: longitude 66.7 deg (vs 75 predicted) and latitude 57.7 deg (vs 55 predicted). The difference is well within the uncertainty range predicted by DJ4ZC, Karn said "Bahn coordinates" is a special coordinate system based on the orbit of the spacecraft and will be addressed in an upcoming Amateur Satellite Report newsletter. Apparently the performance of the kick motor exceeded expectations in terms of thrust. KA9Q points out the delta V on AO-10 was also larger than predicted (by about 11%), even after the longer burn time due to the LIU (Liquid Ignition Unit) wiring error was taken into account. According to Dick Daniels, W4PUJ, the flow rates for both spacecraft were measured on the ground in the same fashion using isopropyl alcohol in place of real propellants. The difference in viscosity between alcohol and the actual propellants could easily account for increased flow rates (and thus increased thrust) on both spacecraft. KA9Q points out these data are important since they "calibrate" the motor's actual performance, helping plan the next maneuvers more accurately. /EX SB ALL @ AMSAT $ANS-177.02 AO-13 Motor OK For More Burns HR AMSAT NEWS SERVICE BULLETIN 177.02 FROM WA2LQQ WARWICK, NY June 25, 1988 TO ALL RADIO AMATEURS BT The AO-13 kick motor burn was the second in-orbit burn performed by any AMSAT spacecraft but the first fully successful one. AO-10's first and only motor burn in 1983 was longer than planned due to a hardware problem. Perigee rose to 3900 km versus the desired 1500 km as a result. Later, due to a Helium leak through a seal, a second burn was found to be impossible. Last week's AO-13 kick motor burn, on the other hand, went perfectly with no deviations except for the higher than expected kick motor performance. Telemetry indicates the pressure loss experienced on AO-10 has not recurred with AO-13. Telemetry channels 09 and, 0D in particular confirm the satisfactory performance. Channel 09 (Helium high pressure) was at about 735 Bars and Channel 0D (Helium low side pressure) was about 14 Bars. Further refinement of AO-13's orbit should now be possible. A second and possibly a third burn can be accomplished whenever the required attitude maneuvers are completed. /EX SB ALL @ AMSAT $ANS-177.03 AO-13 Ranging Proves Accurate HR AMSAT NEWS SERVICE BULLETIN 177.03 FROM WA2LQQ WARWICK, NY June 25, 1988 TO ALL RADIO AMATEURS BT AMSAT's team of ground controllers has begun precise ranging of AO-13 in order to determine its new orbit after the first kick motor burn accomplished last Wednesday. The result is a set of successively more accurate orbital element sets. The data has proved sufficiently accurate to be adopted by official government satellite tracking agencies. AMSAT's orbital determination process begins with range measurements from various command stations using round trip delay time measurements from the earth to the satellite and back. Stations making such measurements at present include KA9Q, DJ4ZC, DB2OS, ZL1AOX and VK5AGR. Once the range data is acquired, a complex number-crunching process begins. A Keplerian element set results which is then checked for "fit" with other tracking data and with AOS/LOS observation reports. Here is a recent product of this process: Satellite: oscar-13 Catalog number: 19216 Epoch time: 88176.00000000 Fri Jun 24 00:00:00.0 1988 UTC Element set: ka9q-3 Inclination: 14.4344 deg RA of node: 242.9507 deg Eccentricity: 0.7012359 Arg of perigee: 183.8892 deg Mean anomaly: 57.3505 deg Mean motion: 2.20055906 rev/day Decay rate: 0 rev/day/day Epoch rev: 19 Semi major axis: 24972.204 km Anom period: 654.379166 min Apogee: 36105.470 km Perigee: 1082.659 km /EX SB ALL @ AMSAT $ANS-177.04 Ariane Launcher Tribute HR AMSAT NEWS SERVICE BULLETIN 177.04 FROM WA2LQQ WARWICK, NY June 25, 1988 TO ALL RADIO AMATEURS BT Another key step towards resumption of the U.S. Space Shuttle flights was taken June 14 with the test firing of a version of Morton-Thiokol's redesigned solid rocket booster (SRB) engine. One final test remains before Space Shuttle flights can resume. June 14th's test firing, fourth of the five required, lasted the required 122 seconds and provided the usual spectacular show as the 126 foot long rocket shook the ground and sent grayish-brown smoke billowing thousands of feet into the Utah skies. Royce Mitchell, Solid Rocket Program Manager for NASA, pegged the test "Extremely Good." Officials for Morton-Thiokol said that, unlike the previous three test firings, no intentional flaws had been introduced into this test rocket motor. They went on to confirm that the final full-scale test firing is planned for late July. The SRB manufacturer plans to introduce several flaws into the joint sections to test the system to its limits. The June 14th test was unique for another reason. It was the first on the newly built $22 million test stand. Hydraulic struts have been added to duplicate steering, flight turbulence and other flight stresses. Data seems to indicate that the engine successfully withstood the simulated worst-case stresses, similar to those experienced in past shuttle flights. A full report is expected within two weeks. Officials said the testing has gone so well that Discovery's two SRB's were mated to an external fuel tank two weeks ago. Discovery was mated to its liquid fuel tank late this past week. If progress continues apace, officials say late August or early September will mark flight resumption. (Story by NW2T) /EX SB ALL @ AMSAT $ANS-177.05 Short Bursts HR AMSAT NEWS SERVICE BULLETIN 177.05 FROM WA2LQQ WARWICK, NY June 25, 1988 TO ALL RADIO AMATEURS BT AMSAT Director Harry Yoneda, JA1ANG, celebrated his 69th birthday on the day AO-13 was born, June 15. Happy Birthday to both. AMSAT Director Bill Tynan, W3XO, is back at home after a couple of days in hospital for angioplasty measures. Bill listened to the AO-13 launch on WA3NAN from his hospital room. Feeling reasonably well, he sends thanks to all who sent him get-well cards/QSLs. Mike Parisey, WD0GML, says he has now completed preparations and placed his new dial-up computer BBS in operation. According to Mike, it will be available full-time on 314-447-3003 and carry the latest AMSAT bulletins and orbital data. It will run the same BBS system used at the W0RPK system Mike says. Operating at 300 or 1200 baud at present, set your modem for even parity, 7-bit word with 1 stop bit full duplex. There is no charge for this service. Handsome posters of AMSAT OSCAR 13 in orbit are now available from AMSAT HQ. Call or write to obtain yours. Here is the AO-10 operating schedule: Through June 30 Mode B MA 30 to MA 230 July 1 to July 31 Mode B MA 25 to MA 235 Aug. 1 to Aug. 15 Mode B MA 30 to MA 240 The satellite will be unavailable for use beginning August 16 because of predicted insufficient solar illumination and reduced battery charge. If "FMing" of signals occur sooner that August 15, DO NOT USE AO-10 please. As always, please use minimum power required for communications. Listen to your nets for later updates, or to AMSAT OSCAR 13 beacons beginning in late July for any changes to this schedule. Here is the FO-12 operating schedule. Mode From (UTC) ---------------- JA Jun 25 0318 JD = Digital mode D 27 0131 JA = Analog mode JA 29 0143 D = All systems off D Jun 30 0049 DI = Systems off except CPU and memory JA Jul 02 0103 D 04 0116 JD* 07 1530 JD 07 1935 DI 08 0143 JD 09 0049 DI 09 2355 JA 13 1409 D 14 1315 JA 16 1328 D 17 1235 JD 20 1356 DI 21 1301 JD 23 1141 DI 24 1020 JD 26 1033 DI 27 1141 JD 30 1100 DI Jul 31 1006 *From 1530 to 1732 UTC, July 7, acquisition of telemetry will be every 2 seconds. The mailbox will be disabled during this interval. The transponders will be off at other times. The actual operating schedule may change due to unexpected situations such as variations in available power. /EX