The Star Charts of Apollo (Part One)
Humans have navigated by the stars, since the dawn of man. Those seemingly stationary pinpoints of light in the night sky provided mariners and aviators the direction home as mankind moved into modern times. It would only be natural to use the stars to determine the proper course of a spacecraft during a voyage into outer space.
Early Earth orbit star charts mimicked the earthbound star charts by having a circular layout with the stars and constellations arranged around the wheel as they would appear in the sky at night. The photograph of an Apollo 9 training star chart is just such an example.
During the Apollo era, stellar navigation was integrated into the digital computer and perfected through the use of a sextant. The diagram below shows how the sextant optical assembly functioned with the DSKY (Digital display and keyboard) to help program the navigation systems and determine the proper course for the Apollo spacecraft. The navigation unit was placed in the lower equipment bay against the wall of the command module for stability and to prevent vibration. The unit consisted of an optical assembly that included the sextant and scanning telescope as well as the DSKY which interfaced with the Apollo Guidance Computer (AGC).
The first major use of the Apollo Guidance Computer came with the flight of Apollo 8. The mission was to journey to the Moon for the first time in the history of mankind. It would also be a test of the MIT designed computer system. The test would be to determine if the Apollo Guidance Computer would be able to navigate the spacecraft to the Moon and back without the help of Earth based guidance assistance.
In the photograph above, taken during the Apollo 8 mission, Jim Lovell is using the scanning telescope to locate a specific star for input into the AGC. Command Module Pilot (CMP) Lovell is sighting through the eyepiece, then he will enter a two digit number that represents the particular star into the AGC via the key pad located in the upper right corner of the photograph. The digital number code for the star would tell the computer one point in space where the spacecraft was located. The triangulation of three star positions would provide an accurate state vector for the Apollo stack that consisted of the command/service module (CSM) and the lunar module (LM). The Apollo 8 mission proved that the spacecraft's navigation computer could be self sufficient on a journey to the Moon.
With the advent of the digital computer that was introduced into the Apollo spacecraft, the star charts changed to accommodate the new system. The star charts were redesigned from the circular chart type to a more rectangular chart. The constellations were aligned on the ellipse. Specific stars were highlighted, named and numbered with a two digit numerical code numbering 1 through 45. If you look closely at the above scan, you will see the stars, their names and numbers on the chart. This star chart from Apollo 10 is an early design that would change to provide ease of use during future missions.
As the missions to the moon progressed, the star charts continued their metamorphosis. Here is a lunar module (LM) chart from the next mission, Apollo 11. Although the grid system is the same, the constellations are heavily outlined and there are no background star fields to confuse the astronauts at key moments. Speed and accuracy were required since the star sightings were usually done during key events like Translunar Insertion (TLI) or Trans Earth Insertion (TEI). This star chart accompanied the crew to Man's first landing on another world.
I caught up with Buzz Aldrin, the Apollo 11 LMP, in New Jersey in 2005. Where I got a photograph with him holding the LM star chart flown on his mission.
This star field chart was for use with the scanning telescope also located at the navigation station inside the command module. This particular page was to show the CMP, Michael Collins, the correct star alignment that he would see through the eyepiece of the scanning telescope. This page showed how the stars should line up to make sure the Apollo CSM was in the right attitude just prior to lighting the Service Propulsion System (SPS) or main engine for TEI. This critical maneuver boosted the crew and their spacecraft out of lunar orbit and back to Earth.
In Part Two of the Star Charts of Apollo, we will show show of the different star charts used in the CSM and LM as well as star charts used on later missions to the Moon.
Early Earth orbit star charts mimicked the earthbound star charts by having a circular layout with the stars and constellations arranged around the wheel as they would appear in the sky at night. The photograph of an Apollo 9 training star chart is just such an example.During the Apollo era, stellar navigation was integrated into the digital computer and perfected through the use of a sextant. The diagram below shows how the sextant optical assembly functioned with the DSKY (Digital display and keyboard) to help program the navigation systems and determine the proper course for the Apollo spacecraft. The navigation unit was placed in the lower equipment bay against the wall of the command module for stability and to prevent vibration. The unit consisted of an optical assembly that included the sextant and scanning telescope as well as the DSKY which interfaced with the Apollo Guidance Computer (AGC).
The first major use of the Apollo Guidance Computer came with the flight of Apollo 8. The mission was to journey to the Moon for the first time in the history of mankind. It would also be a test of the MIT designed computer system. The test would be to determine if the Apollo Guidance Computer would be able to navigate the spacecraft to the Moon and back without the help of Earth based guidance assistance.
In the photograph above, taken during the Apollo 8 mission, Jim Lovell is using the scanning telescope to locate a specific star for input into the AGC. Command Module Pilot (CMP) Lovell is sighting through the eyepiece, then he will enter a two digit number that represents the particular star into the AGC via the key pad located in the upper right corner of the photograph. The digital number code for the star would tell the computer one point in space where the spacecraft was located. The triangulation of three star positions would provide an accurate state vector for the Apollo stack that consisted of the command/service module (CSM) and the lunar module (LM). The Apollo 8 mission proved that the spacecraft's navigation computer could be self sufficient on a journey to the Moon.
With the advent of the digital computer that was introduced into the Apollo spacecraft, the star charts changed to accommodate the new system. The star charts were redesigned from the circular chart type to a more rectangular chart. The constellations were aligned on the ellipse. Specific stars were highlighted, named and numbered with a two digit numerical code numbering 1 through 45. If you look closely at the above scan, you will see the stars, their names and numbers on the chart. This star chart from Apollo 10 is an early design that would change to provide ease of use during future missions.
As the missions to the moon progressed, the star charts continued their metamorphosis. Here is a lunar module (LM) chart from the next mission, Apollo 11. Although the grid system is the same, the constellations are heavily outlined and there are no background star fields to confuse the astronauts at key moments. Speed and accuracy were required since the star sightings were usually done during key events like Translunar Insertion (TLI) or Trans Earth Insertion (TEI). This star chart accompanied the crew to Man's first landing on another world.
I caught up with Buzz Aldrin, the Apollo 11 LMP, in New Jersey in 2005. Where I got a photograph with him holding the LM star chart flown on his mission.
This star field chart was for use with the scanning telescope also located at the navigation station inside the command module. This particular page was to show the CMP, Michael Collins, the correct star alignment that he would see through the eyepiece of the scanning telescope. This page showed how the stars should line up to make sure the Apollo CSM was in the right attitude just prior to lighting the Service Propulsion System (SPS) or main engine for TEI. This critical maneuver boosted the crew and their spacecraft out of lunar orbit and back to Earth.In Part Two of the Star Charts of Apollo, we will show show of the different star charts used in the CSM and LM as well as star charts used on later missions to the Moon.
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