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Erectable S-Band Antenna Deployment

Copyright © 2010 by the Editors of Working on the Moon.
Some photos taken  during an April 1969 training session
were published in the 5 May 1969 issue of Aviation Week and Space Technology.  Photographer James H. Pickerell has given permission for use of those photos in the Journal. Scans courtesy of Journal Contributor Randy Attwood. Last revised 9 October 2012.

S-Band Deployment

The antenna package, including a thermal/micrometeoroid cover
an end cap and various fastenings, had a terrestial weight of 6.1 kg.

When deployed, the umbrella diameter was 3 m. T
he tripod height
and base width were both 1.5 meters.
Illustrations from pages  2-20 to 2-22
in Lunar Module Structures Handout, LM-5


The Erectable S-Band Antenna was first flown on Apollo 11 and was intended to provide a stronger television signal.  Because time during the brief Apollo 11 EVA was so precious, the expected 19-minute deployment of the antenna would have a major impact of productivity.  Consequently, an assessment was made of the first few minutes of the B&W TV signal coming through the LM's steerable antenna.  The signal was deemed adequate, so the Erectable S-Band wasn't deployed.  It was deployed on both Apollo 12 and 14.

Deployment was intended to be easy enough that one person could do it.  However,  training convinced the Apollo 12 crew that they might have to work together when aiming the antenna at Earth.  On both the Apollo 12 and 14 deployments, the astronauts worked as a team doing rough alignments and then, with one of them watching the sighting glass and making small adjustment to elevation using the flexible-cable crank, the other astronaut held the antenna to keep it relatively steady and to keep it from tipping over.  The Apollo 12 and 14 deployments took 15 1/4 and 10 1/2 minutes, respectively.  In both instances, the second crewman took part for about 5 minutes.

Detailed procedures can be found on pages 35 to 39 in the Final Apollo 12 Lunar Surface Operations Plan ( 6 Mb ).


The low weight and high center-of-mass meant that the antenna was easy to disturb.  Evidently, there was enough friction ("stiffness")  in the crank mechanism to cause the structure to move or, even, tip over, unless the astronauts worked together to keep it steady while it was being aligned.  This is probably a case in which mechanical forces became more important relative to gravity than had been the case on Earth.

The Apollo 14 deployment took about 10 minutes 30 seconds versus 15 minutes 15 seconds for Apollo 12.  The difference was due entirely to a much quicker alignment, undoubtedly due to lessons learned for the Apollo 12 experience.


As indicated, the following two-line decal was in the equipment bay to the right of the ladder, just below the stowed antenna.  See Apollo 11 training photo S69-31055.
Offloading Decal

The handle is at the bottom of the package in the following figure, in the astronaut's right hand.  The astronaut's left hand is on the carry bar.  Click on the image for a larger version.  See, also, a detail from S69-31056.

Carrying the
              S-Band Package


The following decal was on the top plate (end cap) of the package as can be seen in a detail from Pickerell photo 01.  The plan was to have the deployment in the field-of-view of the 16mm sequence (movie) camera mounted in the LMP's window.  'Gross pointing' may have involved holding the package upright and turning it around its vertical axis until an arrow on the top plate was pointed at Earth's azimuth (training photo S69-31057).  The antenna was supported on three telescoping legs, which were to be unlocked at this point (Pickerell photo 02).  Finally, the top plate and underlying pad were removed (S69-31150) and discarded (S69-31151).

S-Band Decal 2

As indicated, the next decal was under the top plate.  The antenna's transmitter-receiver was located at the top of a two-section, telescoping mast which, when extended (Pickerell photo 04) and locked, put the transmitter-receiver at the focus of the umbrella-shaped, wire-mesh dish.  Once a second azimuthal alignment was done, the three, telescoping legs were extended upward (training photo S69-31058).  Then, once a tie-down strap was removed from each leg, they were allowed to rotate down, lying horizontal on the ground but attached at pivot points at the bottom of the main antenna body.  At this point, a thermal/micrometeoroid cover (Pickerell photo 05) was removed from from around the bundled umbrella ribs and wire mesh.  Finally, the antenna body was lifted vertically (Pickerell photos 06 and 07, and S69-31156) to get the legs into position and locked.  (During the Apollo 14 deployment, Alan Shepard removed the thermal cover after the lifted the antenna and got the legs locked.)

S-Band Decal 3

The final deployment decal was on one of the legs.  The first steps are to remove the carry bar and a rib protector, as indicated in a labeled detail from training photo S69-31159.  Next, a trigger lanyard was released (S69-31160). This put the trigger about halfway down the legs (Pickerell photo 08), which let the astronaut trigger deployment while keeping his helmet and backpack well out of the way of the quite dynamic unfolding (Pickerell photo 09S69-31162, Apollo 14 training film clip).  Finally, the cable connecting the antenna to the LM was extended out from the MESA and mated to the antenna.

S-Band Decal 4

Antenna Alignment

Alignment in both azimuth and elevation (pitch) was done with a flexible-cable crank.  Apollo 13 training photo KSC-70PC-0016 shows Jim Lovell using the crank.  As detailed on page 38 in the Apollo 12 Lunar Surface Operations Plan, a rough alignment was done first while sighting along the antenna mast (Pickerell photo 12): (e) "Rough align antenna in pitch (CCW rotation of the handle pitches the antenna down). (f) Rough align antenna in azimuth. Pull antenna crank out from housing, then rotate handcrank to change antenna azimuth." Final alignment was done with the aid of a sighting 'glass' mounted on the elevation rotation axis (see the figure below, as well as a detail from training photo S69-17211).

(Click on the image for a larger version.)

Antenna Instability during Alignment

The astronauts found that use of the crank in 1/6th-g disturbed the antenna as a whole and threatened to overturn it.  Consequently, one or both of the astonauts had to hold the legs to keep the structure steady.  A final problem was keeping the OPS antennas clear of the wire mesh, particuarly when sighting along the mast or using the sighting glass.  Detailed commentary on the problems encountered during alignment can be found in the Apollo 12 and 14 Lunar Surface journals starting at 116:01:14 and 114:19:27, respectively.

Details of the Apollo 12 and 14 Deployments

For the Apollo 12 deployment, we have only a few seconds of TV relevant to offloading; otherwise, only the audio and transcript.  These allow approximate times to be determined for some events.  For the Apollo 14 deployment, although the quality of the TV isn't great, we can identify the time of most deployment events from the audio/video record, supplemented by the audio transcript.  The Apollo 14 deployment was the shorter of the two by about 5 minutes, due entirely to quicker alignment.  Clearly, the Apollo 14 crew learned a great deal from the Apollo 12 experience and, pre-flight, probably worked out an effective way to get the alignment done.  Because we have a more complete record of the Apollo 14 deployment, it occurs first in the following table.  Crew comments can be found via the links to the relevant portions of the Apollo 12 and Apollo 14 Lunar Surface Journals

Apollo 14 Ground Elapsed Time
(From Television)
Apollo 14 Time from Start
Apollo 12 Ground Elapsed Time
(From transcript*)
Apollo 12  Time from Start
Apollo 11 Training Photographs
Total Task Times

Start Offload
115:53:42 0

Finish Deployment
114:22:05 10:33
116:08:59 15:15

Deployment details

Start Off-Load 114:11:32
115:53:42 0
Carried package away from bay
Reached deployment location, rough align, remove top plate
Discarded top plate

Has mast raised
115:56:27 02:45
Third leg raised

Leg straps removed, legs released, tripod raised and legs locked

Umbrella cover removed and discarded
115:58:11 04:29
Cover is in the foreground in this A11 training photo, with the carry bar on top of it.
Question from Houston about leg penetration answered

Removed and discarded carry bar and rib protector
Neil has the rib protector in his right hand and will let it slide down the leg on our right.
2nd leg question answered

Al worked on far side of the antenna, probably deploying the trigger lanyard.  Ed brought the connecting cable from the MESA.  Noticed that the antenna was too far from the MESA.

Ed returned to MESA to see if he has pulled the full cable length out.  Returned.

Antenna in final location

Umbrella released but hung up; antenna tipped 90 degrees so Mitchell could free.  Returned to upright.

Didn't get hung up.
Apollo 14 training film clip

Didn't get hung up.
Shepard used the crank to set approximate elevation.

KSC-70PC-0016 (Apollo 13 training photo showing Jim Lovell using the crank)
Mitchell on the sighting "glass".  Shepard adjusted azimuth, looking from behind. They then fine-tuned elevation and got Earth centered.
unnumbered training photo

* Times inferred from the Apollo 12 transcript are more uncertain than those from the audio-synched Apollo 14 TV record.

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