The technology behind the MOCR Group Displays

The two plotting group displays could only be controlled and selected by the assistant flight director (AFLIGHT) or the flight controller "Operations & Procedures" (O&O) by their Manual Select Keyboards (MSKs) on their consoles.
All consoles of the mission controllers in a MOCR were equipped with MSKs to enable the controllers to select a display to be shown on their console TV monitors. These displays could contain data tables, plots, technical diagrams of the spacecraft's subsystems with real-time status data and real-time video feeds.
The MSKs of O&P and AFLIGHT were equipped with thumbwheels to enable them to numerically select displays for their console TV monitors and for the two group plotting displays and the three group video displays.

The seven slide projectors of a projector assembly unit were all controlled by the Projection Plotting Control Electronics. Slide selection commands could be sent to all projectors to have them project a particular slide. To six of the seven projectors, also plotting control signals, could be sent. With those control signals, the progress of spacecraft trajectories in real-time could be shown by the four scribe or plotter projectors, or the location of a spacecraft could be shown with the two spotting projectors.

In the example shown above:

• Only projector assembly unit no.1 is used; projector assembly unit no.2 is switched off.
  
• Projector B (Background reference projector) is projecting two maps using a single slide: a Earth-Moon Transit map and a World map.
• Plotter projector P1 is showing the spacecraft trajectory in real-time on an Earth-Moon Transit map.
  A computer-driven micro plotter was scribing onto an opaque slide, scratching the covering layer, which resulted in a glowing curve projected on the display screen.
• Spotter projector S1 is projecting an icon representing the location of the CSM on a world map.
• Spotter projector S2 is projecting an icon representing the location of the LM on a world map.
• Plotter projector P2 is showing the ground track in real-time on a world map.

The three group television displays could only be changed by the assistant flight director or the flight controller "Operations & Procedures".

The Video Switching Matrix was the hub from which all video information was sent to various television viewers. In this diagram shown above is illustrated how AFLIGHT and O&P could request video information to be displayed on one of their television viewers. All consoles of flight controllers and the operators in the Staff Support Rooms were equipped with a manual select keyboard to enable them to have video information displayed on a particular television viewer of their console. However, only AFLIGHT and O&P were able to have the video information displayed on the group television displays.

In the example shown above, data produced by the RTCC is shown on the left projection TV display. A page of the flight plan is shown on the center projection display. This video information originates from one of the two opaque televiewers in the O&P Staff Support Room. Video footage from the spacecraft is shown on the right projection TV display.

In the picture below is illustrated how the data display image was constructed. To construct a data display image, a video image of a background reference slide, containing static information like tables, diagrams, prompts and table headings, was superimposed on a video image containing the dynamic real-time data from the RTCC. The resulting video data display image was made available via the Video Switching Matrix.

To allow for swift video processing, video images were made from several hundred physical background reference slides and stored in advance. The dynamic data, generated by the RTCC, went through a display generator which formatted and arranged the data to have the layout matched with the corresponding background slides. These video images of the dynamic data were stored in separate buffers. When a particular data display was made available, the video images stored in the two types of storage buffers were merged and sent to the Video Switching Matrix via a TV channel.

The Video Switching Matrix was able to handle 80 input and 160 output channels. About 40 Input channels were assigned to the data displays. So a maximum of 40 TV channels were available for broadcasting other video information.

During an Apollo mission, about 500 data displays could be viewed by the mission controllers and their supporting staff.
Hundreds of telemetry data parameters from the launch vehicle and the spacecrafts (CSM and LM) could be monitored and processed and presented on various data displays.
The data could be classified into five groups:

• Mission command;
• Flight dynamics;
• Systems operations;
• Medical data concerning the crew
• Communications

As an example, a list of 567 data display formats which were used for the Apollo 13 mission is shown on this page.

The challenge was how to make all these 500 data displays available via 40 TV channels.
A sophisticated TV system was used to manage the demand for data displays by swapping data displays. Usage statistics had revealed that at any time, usually at most, 30 different data displays were viewed simultaneously. There were several causes for this user behavior: many of the data displays were mission-phase specific, and the data displays were designed to support various levels of analysis. For a normal Apollo mission there was no necessity to view many of the available data displays, which were designed to look deeper into the behavior of the spacecraft's subsystems and/or its flight behavior when anomalies did occur.

The TV system kept track of the channel saturation rate or system load. An amber alert was given when only 3 to 4 channels were available and a red alert when only 0 to 2 channels were available. Such an alert mechanism urged the users to use the data displays wisely.

For the readers' information
A typical lunar Apollo mission was divided into 20 phases:

1. Launch
2. Earth orbit insertion - spacecraft checkout
3. Trans-lunar Injection (TLI)
4. Transposition and Docking of CSM to LM
5. Trans-lunar coast (TLC)
6. Lunar orbit insertion (LOI)
7. Mid-course correction(s)
8. Lunar Module (LM) descent and landing
9. Luar surface operations & Extravehicular Activitity (EVA)
10. LM liftoff
11. LM-Command/Service Module (CSM) docking
12. LM jettison
13. CSM Trans-earth Injection (TEI)
14. Trans-earth coast (TEC)
15. Mid-course correction(s)
16. Trans-earth EVA (Apollos 15, 16, & 17)
17. Service Module Jettison
18. Reentry
19. Splashdown
20. Recovery

Manual Select Keyboard (MSK) for a triple screen console.

MSK in the data display request mode
(ref.2 page 5, ref.5 timestamp: 6:04)
Purpose: to select a data display.
A flight controller could submit a display request by:

1. depress the MODE key "DISPLAY REQ";
2. entering a four-digit ID number of the display using the thumbwheel switches of the MSK;
3. depress the appropriate ENTER key to select the console TV monitor.

MSK in the TV channel attach mode
(ref.2 page 5, ref.5 timestamp: 6:04)
Purpose: to select a TV channel.
Flight controllers and operators in the SSRs could select a TV channel by:

1. depress the MODE key "TV CHANNEL";
2. entering a two-digit ID number of the TV channel using thumbwheel switches of the MSK;
3. depress the appropriate ENTER key to select the console TV monitor.

TV guide
There was one TV data channel which was dedicated to the so-called TV guide and could be consulted at any time. This TV guide was a list in which was shown which data display was broadcast via which TV channel. The TV guide was updated constantly.
If a user noticed that a particular data display was not listed in the TV guide, he or she had to select the data display using the MSK in the data display request mode.

Credit to Andy Anderson

Display Request Keyboard (DRK) of the EECOM console.

All flight controllers had an MSK on their console to submit a display request using the thumbwheel switch to select the display.

However, the flight controllers RETRO, FIDO, GUIDO, EECOM, GNC, TELMU and CONTROL also had a Display Request Keyboard (DRK) on their console to enable them to quickly request a display by just pressing a key on the DRK.

The DRK had two types of keys: the Field Select (FS) keys (the double row of keys at the top) and the Display Select (DS) keys (the matrix of 32 keys at the center) . This arrangement enabled the controller to select out of a maximum number of 12 x 32 = 384 displays. The purpose of a DS key was set by an FS key.

In the pictures on the left, the appearance of an EECOM DRK is shown when the FS key " CSM EECOM 1" was pressed and when the FS key "plots" was pressed successively.
The DS switches were equipped with projection displays to have their label text changed to reflect the change of their purpose when another FS key was pressed.
In the picture below is illustrated how a projection display works.

A cutaway picture of a projection display made by Industrial Electronic Engineering (IEE).
The device had an optical arrangement of lights, microfilm and lenses to rear-project images onto the small front surface of a key.

Manual Select Keyboard (MSK) for the flight controller "AFLIGHT"

Besides requesting TV data displays for their console TV viewers, O&P and AFLIGHT were the only mission controllers who could request TV data displays for the large three-group projection TV displays.
O&P and AFLIGHT were also the only mission controllers who could request the group projection plotboard displays. Such a request resulted in a pre-programmed response from the RTCC in which the background slide, the plotter and the spotter projectors were selected and the proper plotting data was sent to the Plotting Controller.

Hard copy requests
Mission controllers could request screen prints by pressing the appropriate "hard copy" keys. The prints were produced in a hard copy facility room and were sent to the mission controllers via a pneumatic tube system to the nearest tube station in the MOCR.

1. Mission Control Center Houston
   Familiarization Manual
   PHO - FAM001
   Prepared by Philco, Houston, 30 June 1967

2. Apollo Experience Report
   Flight Control data needs, terminal display devices and ground system configuration requirements
   NASA TN D-7685
   By Richard A. Hoover
   Johnson Space Center, Houston, Texas, May 1974

3. Displays Formats Manual
   PHO - TR515
   Under Contract NAS 9-1261
   Prepared for NASA Manned Spaceflight Center
   By Philco-Ford Corporation, 12 January 1973

4. Apollo 13 mission, EECOM console layout
   https://www.nasa.gov/wp-content/uploads/static/history/afj/ap13fj/pdf-hr/a13-eecom-console.pdf
   Prepared by Andy Anderson
   From the Apollo 13 Mission Documents section of

   The Apollo 13 Flight Journal
   by David Woods, Johannes Kemppanen, Alexander Turhanov and Lennox J. Waugh
   NASA History Division

5. This is Mission Control
   A NASA report about the Mission Control Center (documentary film)
   Produced by A-V Corporation, Houston, 1970
   Source: Internet Archives: https://archive.org/details/ThisIsMissionControl