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MSC View Program / Exhibit

Figure 3c · Scanning telescope, rev 30, 125:15:00 GET — and two errors in the 1969 documents

The printed gimbal angle points the telescope the opposite way, and one star is mislabeled. The figure's own stars show both.

View
Style
Star catalog
-50-50-40-40-20-2000202040405050X, degY, deg-0-5-10-15-20-30-35-40-45-50MenkentAlpheccaAntaresAtriaRasalhagueNunkiAltairDabihPeacockMarsLunar lift-off REFSMMATGimbal anglesI = -89.1°M = 0.0°O = 0.0°

Seen from the spacecraft’s reconstructed position: bodies include parallax, and stars behind the Earth or Moon are hidden.

CSM position: Mission Report Table 7-II "Docking" (128:03:00.0), propagated back 02:48:00.

Residuals: recreation vs. the TN D-6853 (1972) scan (at the figure's own inputs)

BodyScan x, y (°)Recreation x, y (°)Δ (°)Within 2°
Dabih5.20, 38.844.77, 39.490.78Yes
Altair31.19, 32.8731.06, 33.630.77Yes
Peacock-37.61, 25.28-38.03, 25.460.46Yes
Nunki-3.84, 17.43-3.88, 17.950.52Yes
Atria-46.79, -2.90-46.67, -2.510.41Yes
Rasalhague35.70, -2.6135.35, -1.900.79Yes
Antares-5.10, -15.18-5.17, -14.620.56Yes
Mars-3.88, -22.07-4.04, -20.871.21Yes
Alpheratz (printed label; actually Alphecca)47.25, -33.7047.18, -32.980.72Yes
Menkent-25.09, -40.19-24.70, -39.780.56Yes

RMS 0.71°, max 1.21°. An input was inferred from this figure, so this is a consistency check, not independent validation (RMS ≤ 1° and max ≤ 2°: met).

What we found

Both the 1969 Apollo 11 note (69-FM-197, Fig 9.3-8c) and the 1972 report (TN D-6853, Fig 3c) print the gimbal angles for this view as I = 89.10°, M = 0°, O = 0°. Recomputed with those values, the telescope points almost exactly the opposite way: the labeled stars are off by about 150°.

The figure’s own stars say what the attitude really was:

  1. A mislabeled star. Every separation between a pair of labeled stars matches the real sky to within 0.2°, except each pair involving the star printed as “Alpheratz”, which are off by 30–90°. That glyph is Alphecca (Apollo navigation star 26, α Coronae Borealis), within 0.11°. The names are similar, and the labels were typed by hand.
  2. A sign error. A free fit of the other nine labeled stars, converted back into gimbal angles on the same platform alignment, gives I = −88.5°, M = −0.4°, O = −0.1°. The same procedure applied to Figs 3a and 3b returns their printed angles to within 0.3°. The printed magnitude is right to 0.6°, but the sign is wrong.

The recreation shown here uses I = −89.10° with the corrected label. Its ten bodies land within 0.71° RMS (1.21° worst). That is a consistency check, not independent validation, because the sign was inferred from this same figure. To see the attitude the documents print, type 89.1 into the inner gimbal field under “Try it”.

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