# SupportApollo Addon Information re: P23 and Sextant Programming

#### ColonelMcCauley

##### New member
I'm trying to determine how the Sextant is operating in the P23 scenario. Is anyone available who either programmed this, or is familiar with the code?

#### indy91

What exactly do you want to know about? How the sextant works with its split line-of-sight, or how the computer is using the sextant data? Or something else? You are asking a very broad question.

#### ColonelMcCauley

##### New member
What exactly do you want to know about? How the sextant works with its split line-of-sight, or how the computer is using the sextant data? Or something else? You are asking a very broad question.
I asked a broad question to first find someone who knew the Sextant itself. Now I'll ask a specific question. When the trunnion angle is reading 0-deg, what is the angle between the face of the movable Trunnion mirror and the Shaft axis? The documentation describes only the mirror Y-axis, aka Trunnion Drive axis, not the X and Z axes. During the Calibration procedure, the Landmark LOS (LLOS) and the Star LOS (SLOS) are both pointed at a single star, and the two images should be seen as one single image. If the mirror face is parallel to the shaft axis at a 0-degree Trunnion angle, how is this image transmitted to the reticle?

Thanks for replying, and of course for any info you can provide.

Tom

#### ggalfi

##### Well-known member
When the trunnion angle is reading 0-deg, what is the angle between the face of the movable Trunnion mirror and the Shaft axis? The documentation describes only the mirror Y-axis, aka Trunnion Drive axis, not the X and Z axes. During the Calibration procedure, the Landmark LOS (LLOS) and the Star LOS (SLOS) are both pointed at a single star, and the two images should be seen as one single image. If the mirror face is parallel to the shaft axis at a 0-degree Trunnion angle, how is this image transmitted to the reticle?
Based on this image: https://history.nasa.gov/afj/ap08fj/pics/sextant.gif when LLOS and SLOS are pointing into the same direction, the trunnion mirror's normal vector is circa at 45 degrees to SLOS (certainly it depends on the exact orientation of the beam splitter and the prism). What we know for sure from the CDU electronics is that the angle signal of the trunnion mirror's should be taken into account twice as much as any other angle signal fed into AGC (CM Optics Shaft, IMU gimbals, LM RR angles). So a -57° to 57° trunnion range could be covered by a mirror movement between 16.5° to 73.5°.

#### ColonelMcCauley

##### New member
Based on this image: https://history.nasa.gov/afj/ap08fj/pics/sextant.gif when LLOS and SLOS are pointing into the same direction, the trunnion mirror's normal vector is circa at 45 degrees to SLOS (certainly it depends on the exact orientation of the beam splitter and the prism). What we know for sure from the CDU electronics is that the angle signal of the trunnion mirror's should be taken into account twice as much as any other angle signal fed into AGC (CM Optics Shaft, IMU gimbals, LM RR angles). So a -57° to 57° trunnion range could be covered by a mirror movement between 16.5° to 73.5°.
Hello There,
Thanks for the response. I suspect, as you do, that the trunnion angle is 0-degrees when the mirror face is at a 45-deg angle to the shaft axis. In every diagram or line drawing I've encountered, the mirror is depicted at approximately 45-degrees, regardless of the SLOS angle as shown in your link. What I have been searching for is a diagram or verbiage that actually depicts or states the trunnion mirror angle, when the LLOS and SLOS are aligned. The fact that the mirror face (or normal line) angle and trunnion angle are different is an important factor, and should be mentioned, yet it isn't.

Thanks for 2-1 angle ratio info. I actually found a diagram depicting this, and some verbiage as well.

Photos of the vacuum end of the SXT with the cover removed reveal the relative position of the major components. The trunnion mirror and beam combiner are virtually touching at their edges, and the pair of right-angle mirrors are equally close to the opposite side of the beam combiner. The distance between the beam combiner and objective lens are unknown.

Do you have any information as to the dimensions of all the mirrors and beam combiner?

Thanks Again,

Tom

Replies
3
Views
256
Replies
16
Views
2K
Replies
8
Views
721
Replies
5
Views
1K
Replies
1
Views
132