Virtual AGC

Ron Burkey's Virtual AGC code simulates the hardware of the real Apollo Guidance Computer, and can run the same software as was used on a real Apollo mission. This is a separate open source project which is linked into Project Apollo.

The Virtual AGC or vAGC uses software that is believed to have flown on actual missions. Most missions in Project Apollo use Colossus 1A (rev249) otherwise known as Colossus249. It is believed that this software was used for the Apollo 9 mission.

Original Documentation

Some original Apollo-era documentation which may be useful for understanding the operation of the Virtual AGC and the Colossus and Luminary software:

• Apollo 15 Delco Manual -- with information on AGC usage.
• Apollo experience report: Guidance and control systems - Digital autopilot design development

Pre Launch and Service Programs

Programs 00-09 are reserved for Prelaunch and Service programs.

Program 00: CMC Idling also known as "POOH" in astronaut terminology. This is a default state for the AGC. It indicates to the crew the AGC is not engaged in any routines or programs that require crew consideration. It maintains the GNCS in a condition where manual attitude maneuvers can be made by the crew with minimal concern. Finally, it maintains the CMC in a condition of readiness for entry into other programs. Whenever you are not engaged in other programs the AGC should into this state called "Go the POOH"

Program 01: Prelaunch Initialization. This program sets up the CMC and GNCS for preparation for launch. It torques the Stable Member for launch orientation based on the spacecraft position and launch azimuth. This program then automatically starts Program 02.

Program 02: Prelaunch Gyro-compassing. The IMU senses the rotation of the earth while the spacecraft is on the pad. Therefore, this program maintains the IMU id the launch configuration. It also provides the capability to change the launch azimuth due to a change in liftoff time. Lastly, it provides a backup to manually key in that liftoff has occurred.

Program 03: Prelaunch Optical Verification of Gyro Compassing. This program provides a method to verify the Alignment of the Stable Member.

Program 06: CMC Power down. When the CMC is powered down this program puts the AGC in standby. When in standby mode only the Mission clock is updated.

Boost Programs

Programs 10-19 are used in the boost phase.

Program 11: Earth Orbit Insertion Monitor. While the Saturn Rocket uses its own guidance system, the CMC can monitor launch parameters and provide and indication, through the FDAI error needles that the launch is on course. The program is automatically started by Program 02 or by astronaut input.

Program 17: TPI Search. This program is more associated with rendezvous then with boost though it is in the boost group. This program calculates the parameters for the transfer phase to intercept another spacecraft called "Transfer Phase Initiation".

Coast Programs

Programs 20-29 are for navigation. Primarily for tracking other spacecraft, locating and tracking ground targets, and navigating during the transit to to and from the moon.

Program 20: Rendezvous Navigation.

Alignment Programs

Programs 51-54 are used for IMU alignment.

Program 51: IMU Orientation

Program 52: IMU Realign

External Links

• Virtual AGC and AGS Home Page

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