Station Readiness Tests
during Apollo 16

Tape track 1 – Notes by Bryan Sullivan


Explanatory Preamble

Bryan Sullivan
Bryan Sullivan

The recording commences just at the completion of the SRT (Station Readiness Test) for the tracking period for Apollo 16 where the CSM and the LM were both in lunar orbit number four. The spacecraft were separated and the LM had just completed the Descent Orbit Insertion (DOI) manouvre which was carried out behind the moon during the previous orbit.

Moon rise over HSK was about an hour and a half away and the station was entering the H-70 (Horizon minus 70 minutes) countdown to be followed by the H-30 countdown to the AOS (Acquisition of Signal/Spacecraft) or in this case local moon rise. The station was about to commence a period of intensive interface testing with the Goddard Spaceflight Centre (GSFC) and Mission Control Centre at Houston (MCC-H)

Previous activities had included a three hour in-house SRT, conducted in three different phases which had been in progress for approximately two hours.

Phase 1 tested the station intercom(munication) system where all operator positions were manned and a roll-call was conducted by the COMMS supervisor to test each operator’s headset/microphone.

This activity effectively ‘pulled together’ the operations team and gave the station operations console supervisors, OPS 1 and OPS 2, confirmation that all of the forty-odd operator positions were manned.

The station had eight internal voice communication channels referred to as ALPHA loop, BRAVO loop through HOTEL loops. ALPHA was the station’s primary operations coordination loop between the operations console and mainly the section supervisors. BRAVO was an engineering coordination loop for lengthy conversations regarding equipment problems. CHARLIE loop was mainly for the OPS 2, Telemetry and Computer supervisors to coordinate data flow operations. The other loops were for local communications within each section. [See these pages from the HOD relating to Phase 1.]

There were three external channels or ‘nets’ referred to as NET1, NET2 and NET3. The NET1 was for the astronauts to converse exclusively with the CAPCOM (Capsule Communicator) flight controller at MCC-H. The NET2 was for the operations coordination between the tracking station(s) and the other MCC-H flight controllers. NET3 was for coordination of pre-tracking testing as well as facilitating ‘out-of-conference’ or ‘off-net’ conversations with individual stations.

The SRT Phase 2 tested all of the individual stand-alone subsystems of each section – Unified ‘S’ Band (USB), Ranging, Timing, Telemetry, Recorders, Video, Computers and Communications. These activities involved diagnostic testing, alignment and calibration checking of all units within each subsystem.

Phase 3 SRT involved the testing of integrated subsystems to verify the many hardware interconnections with the a vast array of peripheral units such as the decommutators, up-data buffers, pulse amplitude modulation (PAM) processors, analog multiplexer quantizers (AMQ) and the station timing system for GMT signals as well as consoles, printers and teletype (TTY) machines.

The next major activity was the CADFISS (Computation And Data Flow of Integrated Sub-Systems) testing where the real-time CADFISS computers at the GSFC tested each tracking station in turn prior to handing them over to the Mission Control Center. Specific tracking, ranging, telemetry and command data was exchanged and compared with known or predefined values. This part of the SRT was conducted under the GSFC Network Operations Manager (NOM) in a sequence as per the mission tracking support schedule.When the NOM was satisfied that all CADFISS testing was ‘GO’, the station was configured into the MCC-H Real Time Computer Complex (RTCC) via the world wide NASA Communications System (NASCOM).

The station then moved into the H-70 interface testing countdown, with MCC-H conducting a further series of data flow tests which were more aligned with the upcoming events or phase of the mission timeline. Specific telemetry data and biomed formats, spacecraft commands and tracking data that were more closely tailored to give the flight controllers confidence that the stations were correctly configured and ready to support the upcoming events in the mission flight plan.

The time from the commencement of the SRT Phase 3 through the H-70 testing and up to the start of the H-30 countdown was one of the busiest and most activity intensive periods of the Apollo tracking day.

Listen to the audio of Part 1 of the tape – 14 min 32 s – 1.8MB mp3 file.

(Opens in a new window.)


Personnel heard on this tape (in order of appearance):

OPS1 Bernard Smith
SIM Neil Sandford
OPS2 Bryan Sullivan
SB1 Frank Campbell
SB2 Neil McVicar (at HSKX, Tidbinbilla)
1218 (Computers) Don Loughead
DATA Bill Perrin
COMMS Keith Hiscock
CRO Paul Oats

Start of Tape Track # 1

Times in red are from the start of the audio file.

00:00. At the start of this audio recording we hear OPS1 concluding video testing where simulated TV signals from the station’s simulation (SIM) console are processed by the video processing system.

00:14. OPS2 announces the end of SRT Phase 3 testing and advises the USB supervisors, SB1 and SB2, of the required configuration for start of the H-70 testing.

00:50. OPS2 requests changes in the Univac 1218 computers from SRT to mission support configuration.

01:16. OPS2 authorises an in-house test of the CADFISS analog magnetic tape with the telemetry decomutators (DECOMS) and the computers prior to the H-70 start.

01:33. OPS2 requests the COMM supervisor to configure all of the station’s external data lines for interface testing.

01:50. OPS2 initiates an end-of-file (EOF) mark on the command history tape while the computer operator visually verifies the tape movement. Also the computer operator verifies a dump of the command activity log file (LOG DUMP) to magnetic tape.

02:20. OPS2 requests a LOS/ROS (loss of signal/return of signal) file mark on the telemetry log tape, however the decommutators were not inhibited from the computers as the TLM supervisor was still testing the CADFISS tape.

02:40. OPS2 verifies that both of the up-data buffers (UDBs) are in ‘safe’ mode in order to prevent spurious command data being sent to the USB power amplifiers (PAs or transmitters).

02:47. The simulation console operator (SIM) advises OPS2 that all of the SRT patches are removed from the mission support equipment and that all radio frequency (RF) signal sources (test oscillators and signal generators) are turned off.

03:00. The COMMS supervisor configures Net 1 to normal, thereby enabling HSK to hear the conversations between the astronauts and the MCC-H CAPCOM (CAPsule COMmunicator) as well as the periodical mission summaries from ‘Apollo Control’ public relations.

[Conversations between Carnarvon and Goddard, and Goldstone and Goddard are also heard, as well as Public Affairs commentary in the background.]

04:26. GODDARD OPS calls HSK ‘off-a-net-3’ meaning a direct connection with HSK without any other stations hearing, i.e. Net 3 is now ‘out of conference’. GODDARD OPS checks the HSK status for the start of the H-70 testing.

04:41. OPS1 advises that ‘we are GO for interface’ and that the status for tracking (CADFISS) is: (HSK or ‘prime’ site) SYS-1: CSM, SYS-2: LM and (HSKX or ‘wing’ site [Tidbinbilla]), SYS-3: CSM, SYS-4: LM.

05:02. OPS2 announces that the command interface test has started. Command data is now being received from the CADSFISS computers by the HSK Univac command computer.

05:30. The CADFISS Real Time Command (RTC) operator is testing the ‘uplink’ path through the UDBs to the PAs (radiating into dummy load), through to the verification receivers, back to the telemetry computer and back to the CADFISS computers.

Telemetry testing commences with specific data formats for engineering and biomed that will be required for the upcoming mission support period.

06:23. CADFISS TM (Telemetry) requests HSK to change the biomed telemetry format.

07:00. CADFISS RTC requests access to the ‘wing’ site (HSKX [Tidbinbilla]) after completion of the ‘prime’ site command testing.

08:18. NETWORK hears that Bermuda (BDA), Hawaii (HAW) and Mila (MIL, Merrit Is.) have configured their teletype (TTY) circuits back to normal following their support of the DOI data playback (Descent Orbit Insertion) manouvre of the LM.

COMM MGR requests Hawaii to send a ‘number comp’ (number comparison test) on their bravo channel to verify that their TTY configuration is correct.

Each station had two teletype circuits, one for sending low speed tracking data and the other for receiving low speed command data, referred to as the alpha and bravo channels.

08:53. RTC advises HSK that command interface is GO whereby OPS2 sends a history transmission of all the commands processed during the test via the high speed data line, he then writes an end-of-file on the command history magnetic tape and initiates a dump of the activity file to the log magnetic tape.

09:36. OPS2 advises COMPUTERS that the UDBs are in ‘safe’ mode where they will remain until they are switched back to ‘operate’ mode during the H-30 countdown.


With the completion of the command interface testing both HSK and HSKX USB sections prepare for their tracking CADFISS tests including boresight alignment, predefined antenna movement (tracking) and ranging equipment. These tests are usually coordinated between OPS1, SB1 and SB2.


09:58. OPS2 requests COMMS to reconfigure the RO (receive only) teletype to normal from its support of the low speed CADFISS tracking data test.

10:26. GODDARD OPS prepares to start telemetry testing predefined formats of spacecraft engineering parameters and astronaut biomed data from the CADFISS magnetic tape through the Univac telemetry computer and out via the Data Transmission Units (DTU), modems and the high speed lines back to GSFC.

10:43. COMMS supervisor reports the arrival of a teletype cue, where OPS2 requests the DATA supervisor to ‘roll the (CADFISS telemetry) tape’.

11:12. CADFISS TM queries the patching of the telemetry formats after which DATA supervisor tells OPS2 that the analog magnetic tape recorder was running at the wrong speed.

12:44. The DATA supervisor is discussing the track 11 SM4/6 CSM hi-bit rate and FM biomed thru the AMQ (Analog Multiplexer Quantizer) processor. Here he is referring to data from the scientific experiments within the SIM bay on the CSM service module of the spacecraft. This telemetry was downlinked along with biomed data on a frequency modulated (FM) subcarrier and processed thru the AMQ and then by the Univac telemetry computer.

Regarding the ‘inquisition’ into the operator error with the CADFISS tape, maybe OPS2 was wondering to whom the Fickle Finger of Fate should point.

14:00. SB2 advised OPS1 that the wing site ranging computer has locked onto the CADFISS test data.

14:18. OPS2 advises the DATA supervisor of a successful test of the CADFISS biomed data formats.

Note the sounds of the teletype printers clattering away with hard-copy of the various test results.

End of audio tape part 1.


Go to Part 2.


Notes by Bryan Sullivan. Times, Colin Mackellar.