Amsat Oscar-10
W4SM's "非公式" Web Page
打ち上げ前の実物
Welcome to my unofficial AO-10 Web page.
Thanks to Paul Willmott for sending the drawing of AO-10 now shown above, to James Miller for pointing out that the AO-13 drawing initially shown was just the AO-10 drawing with an S-band helix added in, and to Peter Guelzow for pointing me to the Amsat-DL Web site http://www.aball.de/~pg/amsat/ from which the above picture was obtained.
I'll use this site to post what is currently known, estimated, or "guesstimated" regarding AO-10. As time permits, a history of AO-10 will be added.
Current Status: 1998,09,15
Beacon signals on AO-10 are currently undetectable except with DSP software. Thus, it appears that AO-10 is now deep into another of its "sleep phases." The current phase is unexpected given guestimated solar angle from the last sleep period. This suggests strongly that AO-10 is no longer attitudinally stable. Future stable calculations of ALON/ALAT may not be possible. However, I would expect AO-10 to return to semi-usable status within another month or so.... maybe faster if it's attitudinal instability moves it towards a better solar angle. Stay tuned for further developments and keep your fingers crossed for P3D.
"SEE" AO-10's weak beacon with digital signal processing.
Even though you can't currently hear the beacon, it's there very weakly, as several individuals have demonstrated using digital signal processing. To view a gif file screen image of the beacon's output using FFTDSP software Click Here. This file was obtained by Mike West / WL7BQM.
Current "Solar" Eclipses
AO-10 is currently experiencing periods of darkness due to entering the earth's shadow around perigee. These are periods currently lasting approximately 27 minutes, beginning at MA = 253 and lasting until MA = 7. The transponder and beacon go dead almost instantly when AO-10 enters the earths shadow. These eclipses actually continue through the end of the year. They become of shorter duration until November 7 (12 minutes) and then begin lengthening again, reaching 75 minutes in duration on December 31st (MA 34 to 62).
Last "Lunar" Eclipse
On 1998,03,28 beginning at 1133 UTC, AO-10 had its sunlight partially blocked by the moon when it was at MA 60-78. The maximum occlusion was only about 11%, so it is doubtful that any change in the quality of the downlink signals could be noticed.
Antenna Configuration
As noted above, AO-10 currently seems to be using its hi-gain antennas. When the switch to the hi-gains may have occurred is unclear. The change was presumably caused by a "bit glitch" affecting the antenna latching relay. Listening to the beacon will occasionally demonstrate short runs of nonsensical PSK telemetry, indicating that there are "instabilities" in the system.
AO-10の近地点引数（ArgP Argument of Perigee)
AO-10の軌道傾斜角は比較的小さいために、その近地点引数 ArgPの変動はAO-13に比べてはるかに大きくなります。現在の値は211度ですから、遠地点は北半球上にあります。ArgPは0.28度/日の割合で増え、遠地点は一番南になるArgP=90度から徐々に北に移動してきました。遠地点はさらに北に移動し、1998年12月1日にはArgP=270度となってもっとも北になります。1998年と1999年のほとんどにおいて遠地点は北半球上にあります。
簡単な履歴
AO-10 は1983年6月16日にフランス領ギアナのクールーからArian-2ロケットで打ち上げられました。初期の小さな問題により、傾斜角の高いモルニア軌道に投入することはできず、傾斜角26度の軌道に投入されました。AO-10の軌道はとても安定していますから（数100年は）AO-13のように大気に再突入するようなことはありません。AO-10が製作されたときには放射線強化されたメモリーは手に入らなかったため、1986年の12月に高い放射線レベルによりIHUは機能を失いました。それ以来、衛星はコントロール不能となり、Z軸を中心としたスピン速度は徐々に低下しています。モードBが選択されたままとなっており、ハイゲインアンテナが使われているようです。搭載された電池は開放状態で使用不能になっており、AO-10の電源は完全に太陽電池に依存しています。このため衛星が“食”に入るとトランスポンダは直ちに機能を停止します。
なぜ AO-10 は時々“寝て”しまうのか？
AO-10's usually twice yearly "sleeps" are not due to solar eclipses. A solar eclipse, from the satellite's point of view, occurs when the earth comes between the satellite and the sun. This does indeed happen during certain seasons of the year on virtually every orbit, but for rather short periods of time. The phenomenon happening with AO-10's sleeps is related to the fact that spin-stabilized satellites always point at the same spot in space (allowing for minor perturbations). As the satellite, along with the earth, rotates around the sun, the sun, appears to the satellite to rotate around it. If the orientation isn't changed, and assuming ALAT is within the range of the ecliptic (solar plane) then twice a year the sun will hit either the antenna end or the motor end of AO-10. During this time, the solar panels will be in darkness, or at least at light levels insufficient for adequate power generation. However, there's sun on the END of the satellite, so it's not in an eclipse. The batteries on AO-10 are totally dead.... when it goes into a true eclipse it instantly loses power and power/transponder instantly returns a bit later (minutes) when the satellite emerges from the earth's shadow.
Why not use AO-10 when signals are "FMing?"
The chances of damaging AO-10 by uplinking during "FMing" are probably remote. The caution mainly stems from a theoretical consideration. AO-10's latching relays are currently set to the hi-gain antenna and the transponder is on in Mode-B configuration. Each time there's a power spike the chance exists that the IHU could have a "seizure" and blurt out a pulse to switch the antennas, switch the transponder off or whatever. Of course these spikes occur every time we come out of eclipse, but the idea is to do what we can to minimize the number of power spikes. Occasionally spikes have "activated" the IHU in the past and caused the beacon to send out nonsensical data rather than the current constant carrier for short periods of time. One of these spikes in the last year or so apparently switched AO-10 to the hi-gain antenna, so such things can happen. I suppose there are also some considerations regarding the effects on the transponder of operating it so far off its normal voltage/current curve, but, again, this doesn't seem to have caused a problem after many years.
AO-10's ALON/ALAT
Because it's IHU has been dead for many years, AO-10's attitude cannot be precisely determined. However, it's orbit is well known and if we assume that at the mid point of its "sleep" cycles, one end of the S/C is pointed directly at the sun, we can guesstimate an ALON/ALAT. These calculations may be off by at least +/- 20 degs. Also, we don't know, based on illumination alone, which end is pointing at the sun, so the ALON/ALAT's given could be reversed (ALON +/-180, ALAT change sign). The last well documented deep sleep cycle seemed to have it's low point on about 5/25/97. On that date the sun was at SAZ(ALON)=158, SEL(ALAT)=47 with respect to AO-10's orbital plane. Thus, if the satellite were pointing directly at the sun on 5/25/97, it's ALON/ALAT would have been 158/47. Once the current sleep cycle is over (1998-09-15), I'll attempt to recalculate an ALON/ALAT. However, as noted above, I am not confident that AO-10 is attitudinally stable any longer due to its very slow rotation.
James Miller (G3RUH) has developed a suite of software programs running on the Acorn Risc Computer systems for commanding and orienting AO-13 and other P3 satellites. I have modified and "ported" many of his routines to run in Windows format on PC-type machines, and to allow use with multiple satellites. The following Tables were derived from my modifications of James' software. Any errors are mine.
The chart below shows the effect of ALON/ALAT on solar illumination on 1998,03,28. The center of the "hole" at the upper right is approx. ALON/ALAT 70/30 may be thought of as the sun's position (Saz/Sel). The "mirror" hole is at the reciprocal values of ALON/ALAT 250/-30. The numbers listed are the sun's angle on the solar panels (0 = directly overhead, maximum illumination). Negative numbers indicate the sun favoring the antenna end of the satellite. Positive numbers mean the sun is towards the motor end.
A spin stabilized satellite should always point at the same place in the celestial plane. ALON/ALAT, however, is based on orbital plane coordinates, so as the orbit changes, primarily due to precession of RAAN and ArgP, the values of ALON/ALAT change, even though the S/C is still pointing at the same celestial point.
The table below shows the weekly effect of orbital precession on AO-10's ALON/ALAT, given an ALON/ALAT of 135/32 on 1998,03,29. Note that the illumination drops off rapidly over the next few weeks.
Has AO-10's Attitude CHANGED?
The last sleep phase for AO-10 that I'm aware of centered on 1996/2/10. At that time the solar location in the orbital plane was SAZ/SEL = 113/-40. If AO-10's ALON/ALAT = 293/40 at that time (SA = 90, Ill = 0%), then by orbital plane precession effects alone, on 5/25/97, ALON/ALAT should = 244/14, SA = 13 deg, illumination = 97%, which clearly can't be correct so it WOULD APPEAR that AO-10 is no longer highly attitude stable....which renders the above tables of questionable value! This is in agreement with the simple observation that the six month cycle of sleep/wake has been disrupted, as no "sleep" occurred this February. The currently slow spin rate of AO-10 is probably the best explanation for the instability, especially if it continues to show apparent heading changes. If the heading once again remains stable, other "one time" possibilities for attitude disruption may be in effect.
AO-10's Spin Rate
The spin rate of AO-10 appears to be approximately 1.5 RPM. This is based on observations that I have made on multiple occasions, based on QSB cycles of the beacon. When the attitude of AO-10 is such that the antenna is partially blocked by the S/C, the QSB comes in 13+ second intervals. Two of the intervals are exactly the same in duration and depth, the third is distinctly different. The repetition of this cycle is convincing that a set of three fades = 1 revolution, not 3 revolutions. Thus 1/(13 secs * 3)/60 = 1.5 RPM. The three fades/revolution are due to the tri-lobed shape of AO-10. The reason for the dissymmetry of one fade is not clear, but may be related to damage sustained when AO-10 struck a portion of its launcher early in its life.
Why has AO-10's Spin Rate Decreased?
The best reason for this is "magnetic damping" as the conductive body of the S/C crosses the earth's magnetic field lines, especially around perigee. The phenomenon was quite pronounced with AO-13, because of its lower perigee.
Next AO-10 Lunar Eclipse
AO-10 is occasionally eclipsed by the moon rather than by the earth, the much more common occurrence discussed above.
This Table outlines the next lunar eclipse affecting AO-10 on 1998,08,22. A maximum eclipse of 36% is reached, but since the eclipse occurs near perigee, it lasts less than 15 minutes. Times are in UTC.
Typical AO-10 QSO
What does an AO-10 downlink sound like if you've never heard it before?"Click here to download a short "wav" file of an AO-10 QSO courtesy of Tony Bombardiere - AB2CJ.
AO-10 MODE-B TRANSPONDER
- INVERTING TRANSPONDER (LSB uplink, USB downlink)
- UPLINK PASSBAND:
- 435.027 - 435.179 MHz
- DOWNLINK PASSBAND:
- 145.825 - 145.977 MHz
- TRANSLATION EQUATION:
- Downlink Freq = 581.004 - Uplink Freq.
- BEACON: 145.810 MHz (continuous carrier)
AO-10 SMOOTHED KEPLERIAN ELEMENTS
- WinKeps Program by W4SM based on modified algorithms from G3RUH
- Based on: 30 sets of elements
- From: 1997/268.02
- To: 1998/207.9
Satellite: AO-10
Catalog number: 14129
Epoch time: 98207.89601271
Element set: 557
Inclination: 26.9366 deg
RA of node: 76.3319 deg
Eccentricity: 0.5987386
Arg of perigee: 236.166 deg
Mean anomaly: 52.4627 deg
Mean motion: 2.05878974 rev/day
Decay rate: 1.38e-8 rev/day^2
Epoch rev: 11369
Checksum: 344
# of Site Visits = 2665
E-mail to: sem2r@virginia.edu
Maintained by: Stacey E. Mills, W4SM
Last Modified: 1998,09,15 @0200 UTC