PARKING ORBIT

The USNS Vanguard had relayed communications as Apollo 11 entered orbit, then there was a hiatus until the spacecraft came within range of the tracking station on the island of Grand Canary, off northwest Africa. A valve in the command module had opened during the ascent through the atmosphere, and while its regulator had slowly allowed the cabin pressure to fall to 5 psi the environmental system started to increase the oxygen ratio and slowly purge the nitrogen that had been present to reduce the risk of a fire at sea-level pressure. Simultaneously, the pressure in the suits had also been reduced. For several hours prior to launch, the astronauts had been breathing oxygen at sea-level pressure to cleanse their bloodstreams of nitrogen, and on completing the post-insertion checklist they were able to doff their helmets and gloves, which were stowed in canvas bags. Despite the pre-breathing, Collins found that his left knee ached, as it had during his Gemini 10 mission, but in view of that experience he expected the discomfort to fade in a few hours.

‘‘Apollo 11,’’ McCandless called, ‘‘this is Houston through Canary.’’

‘‘Post-insertion checklist is complete, and we have no abnormalities,’’ reported Armstrong.

Insertion occurred at T + 709.33 seconds; this being S-IVB cutoff plus 10 seconds to allow for engine tail-off and other transient effects.

As they left Canary behind, Collins unstrapped himself from his couch and went to the lower equipment bay to unstow the equipment that they would require. In a gravitational field the vestibular system of the inner ear facilitates a sense of balance, but in weightlessness the fluid that yields these cues sloshes about freely. Despite having performed aerobatics a few days previously to ‘condition’ himself, he avoided sudden head movements that might induce disorientation.

‘‘Hey, Buzz?’’ Collins called.

‘‘Yes?’’

‘‘How would you like the camera?’’

‘‘Okay.’’

‘‘Here’s a Hasselblad for you.’’ The Hasselblad for internal use was fitted with an 80-millimetre lens.

‘‘Just a second!’’

‘‘I’ll just let go of it, Buzz; it’ll be hanging over here in the air – it’s occupying my couch.’’

A minute later, Collins asked, ‘‘Buzz, did you ever get that camera?’’

‘‘Yes.’’

‘‘Are you ready for 16-millimetre?’’

‘‘Yes. How about a bracket?’’

‘‘Neil will give you the bracket.’’

Collins unstowed the 16-millimetre Maurer ‘sequence camera’, also known as a Data Acquisition Camera, and gave it to Aldrin, who mounted it on a bracket in the right-hand forward-facing window ready to film the retrieval of the LM following TLI. It could run at 1, 6 and 12 frames per second on automatic, and 24 frames on semi-automatic, with shutter speeds of 1/60th, 1/125th, 1/500th and 1/1000th of a second.

‘‘I’m having a hell of a time maintaining my body position down here,’’ Collins complained, ‘‘I keep floating up.’’

After briefly checking in with Houston through the relay site at Tananarive on the island of Madagascar in the Indian Ocean, they crossed the evening terminator. As the ‘platform’ of an inertial measurement unit tends to drift out of alignment, it requires frequent resetting. While they were in Earth’s shadow, Collins was to run computer program 52 (referred to as ‘P52’) and take star sightings with the sextant in the wall of the lower equipment bay to realign the platform. At orbital insertion, the long axis of the vehicle was aligned with the velocity vector, with the sextant aimed towards space, and the S-IVB had established a pitch rate designed to maintain this ‘orbital rate’ attitude.

The platform used a nest of three gyroscopes and associated accelerometers to measure the spacecraft’s attitude and velocity with respect to the orthogonal axes of a coordinate system in a specified frame of reference. Different frames were to be used at different times during the mission, each specified by a ‘reference to the stable member matrix’ (REFSMMAT). As the spacecraft rotated, the platform tended to remain fixed in inertial space and the gimbals rotated to compensate. The platform, aligned to a REFSMMAT – the ‘stable member’ against which the gimbals tracked the attitude of the spacecraft – was the one reference that remained in the same position relative to the stars irrespective of what the spacecraft did. For the start of the journey, the REFSMMAT was defined (in part) with respect to the line from the centre of the Earth through the launch site at the time of liftoff and also with respect to the flight azimuth. This frame would be retained through to TLI. The optical system had a telescope and a sextant. The telescope gave a 60-degree field of view, without magnification, and was intended to be used to identify a constellation and aim the coaxial sextant in the direction of a given star. The sextant’s 1.8-degree field of view was magnified 28 times in order to make precise sightings. If the platform lost its sense of direction – which would occur if a pair of its three gimbals became co-aligned, locking them together (a condition appropriately known as ‘gimbal lock’) – Collins would run through this procedure to realign the platform from scratch. But when he merely wished to find out whether the system really knew its attitude, he would simply ask the computer to aim the sextant at a particular star, and check to see how far it was from the centre of the field of view, then mark its true position. With sightings on two stars, the computer could refine the alignment of the platform. As confirmation, he would then ask the computer to aim the sextant at a third star, which should then appear precisely centred in the field of view. With knowledge of its attitude and the ‘state vector’ specifying the spacecraft’s position and velocity, the computer could, at least in principle, calculate all the manoeuvres necessary to conduct the mission independently of ground support.

Explorers have been navigating on Earth by telescope and sextant for centuries. The computer served essentially the same function as the chronometer. The inertial system not only acted as a compass, but also measured acceleration, which was not a quantity needed on the surface. The digital computer was the technological marvel – a decade earlier, navigating in space would have been a considerably more manual process. Indeed, it could be argued that a lunar landing mission would not have been very practicable prior to the 1960s. The display and keyboard (DSKY, pronounced ‘disky’) of the computer was supplied by the Raytheon Company. It had a power supply, decoder relay matrix, status and caution circuits, a 21-character display unit, and a 16-button key pad with the digits ‘0’ through ‘9’, ‘VERB’, ‘NOUN’, ‘CLEAR’, ‘ENTER’, ‘PROCEED’ and ‘KEY RELEASE’. The executives, developed by the Instrumentation Laboratory of the Massachusetts Institute of Technology, were named ‘Colossus IIA’ for Columbia and ‘Luminary’ for Eagle, and used ‘programs’, ‘nouns’ and ‘verbs’. Verbs were the instructions to do something in the context of a program, while nouns represented the structures that were to be operated upon. For example, if Verb 06 Noun 62 was entered, the verb meant ‘‘display in decimal’’ and the noun indicated what was to be displayed (in this case three numbers of the spacecraft’s inertial velocity, vertical speed and altitude). Some programs had many verb and noun pairings. Numerical data took the form of five-digit quantities, scaled to fit and incorporating an implied decimal point. When a key was depressed, the appropriate item illuminated on the display. A verb would be flashed if the computer wished to attract attention when awaiting crew input. There were two DSKYs in Columbia – one on the main control panel, and the other in the lower equipment bay by the navigational instruments – and one in Eagle.

Star sightings were impractical while the spacecraft was in daylight because the particulates that the vehicle shed, and which floated alongside it, reflected sunlight and made it difficult to see the stars. But this material became invisible in Earth’s shadow. After jettisoning the external cover of the optical system and inserting the eyepieces into the sextant and telescope, Collins peered though the telescope. The view was not encouraging. “f think f am seeing the horizon, but I’m far from being dark-adapted; it’s hard to tell.’’ He installed the handles that were to enable him to hold his weightless body in position to use the instruments. Finally, to cover his left eye while viewing with his right, Collins donned a small plastic patch attached to an elasticated string. The computer knew the celestial coordinates of 37 naked-eye stars that were widely distributed across the sky, each identified by an octal (i. e. base 8) number.

With the vehicle maintaining a fixed attitude with respect to Earth while they remained in low parking orbit, there were only a few reference stars available for this initial P52 check, and the mission planners had decided which ones he should use. Collins told the computer to aim the optics towards star 30, Menkent in the constellation of Centaurus. As the view through the telescope was poor, he went straight to the sextant. The star was slightly ‘off. He centred the cross hairs of the sextant on the star and instructed the computer to record its true alignment. Then he asked for star 37, Nunki, in Sagittarius, checked it, and marked it. The Apollo sextant was more practicable than the hand-held version he had tested on the first orbit of Gemini 10, when John Young, his commander, had dubbed him ‘Magellan’ after the captain of the first ship to circumnavigate the world. Having marked two stars and told the computer to update the platform, Collins instructed it to find star 34 as a final check. ‘‘Atria is there in the sextant, but it’s not dab-smack in the middle.’’ He asked the computer to display the alignment discrepancy as a fraction of a degree. ‘‘0.01, Goddammit! Now that’s enough to piss a body off.’’ Glenn Parker, an instructor at the Cape, had bet him he would not achieve an accuracy better than 0.02 degree, and Collins had been sure he could attain a perfect 0.00 alignment. Finished with the optical instruments, he removed and restowed the eyepieces.

Carnarvon on the southwestern coast of Australia was operating three tracking systems to ensure that the parameters of the orbit were accurately measured, to enable Dave Reed, the flight dynamics officer in Houston, to calculate the TLI burn. After McCandless confirmed that there were no issues involving the S-IVB that might threaten the continuation of the mission, Collins, judging his bet to have been a tie, asked McCandless to pass on a message, ‘‘Tell Glenn Parker at the Cape that he lucked out – he doesn’t owe me a cup of coffee.’’

A black-and-white Westinghouse television camera with scan rate of 10 frames per second and 320 lines of resolution was carried on Apollo 7 and Apollo 8 with good results. A camera using the sequential colour technique was tested by Apollo 10, and issued to Apollo 11. Passing over Australia, Collins unstowed the camera and its ancillary apparatus and plugged in the power and signal cables. The camera was a rectangular box with a lens protruding from the front end. The monitor to enable them to see the field of view in order to verify the focus and lighting was the same width, about half the length, and slightly thicker, and had a small display

Table: Apollo navigation stars Popular Name Code (octal) Official Name Alpheratz 01 alpha Andromedae Diphda 02 beta Ceti Navi[9] 03 epsilon Cassiopeiae Achernar 04 alpha Eridanus Polaris 05 alpha Ursa Minor Acamar 06 theta Eridani Menkar 07 alpha Cetus Mirfak 10 alpha Persei Aldebaran 11 alpha Tauri Rigel 12 beta Orionis Capella 13 alpha Aurigae Canopus 14 alpha Carinae Sirius 15 alpha Canis Majoris Procyon 16 alpha Canis Minoris Regor* 17 gamma Velorum Dnoces* 20 iota Ursae Majoris Alphard 21 alpha Hydrae Regulus 22 alpha Leonis Denebola 23 beta Leonis Gienah 24 gamma Corvi Acrux 25 alpha Crux Spica 26 alpha Virginis Alkaid 27 eta Ursae Majoris Menkent 30 theta Centaurus Arcturus 31 alpha Bootis Alphecca 32 alpha Corona Borealis Antares 33 alpha Scorpii Atria 34 alpha Trianguli Australis Rasalhague 35 alpha Ophiuchi Vega 36 alpha Lyrae Nunki 37 sigma Sagittarius Altair 40 alpha Aquilae Dabih 41 beta Capricornus Peacock 42 alpha Pavo Deneb 43 alpha Cygni Enif 44 epsilon Pegasi Fomalhaut 45 alpha Piscis Austrinus

screen on one end. The flight plan called for a test of the system by sending to the Goldstone station of the Manned Space Flight Network, situated on a dry lake in the Mojave Desert near the town of Barstow in California. Having had no in-flight anomalies, they set off across the Pacific Ocean with 20 minutes of free time.

“How does zero-g feel?” Armstrong enquired of Collins, who was the only one to have left his couch.

“I don’t know,” Collins mused. “It just feels like we’re going around upside down.”

Indeed, they were, because the S-IVB was maintaining them in a ‘heads down’ attitude, but Collins was referring to the sensation of ‘full headedness’ that arises from the accumulation of blood in the head with the onset of weightlessness.

Passing south of Hawaii, the eastern horizon began to glow.

‘‘Stand by for sunrise,’’ announced Collins.

‘‘Neil hasn’t seen many of those,’’ pointed out Aldrin. Gemini 8 had performed an emergency return after only a few orbits, during which Armstrong had been too preoccupied to appreciate sunrise.

‘‘We haven’t got too many of them on this flight, so you might as well enjoy it while you can,’’ Armstrong advised.

By now the view ahead was a spectacular arc of colour.

‘‘Jesus Christ, look at that horizon!’’ Collins exclaimed.

‘‘Isn’t that something?’’ Armstrong agreed. ‘‘Get a picture of that!’’

‘‘Has anybody seen a Hasselblad floating by?’’ Collins asked. ‘‘It couldn’t have gone far, a big son of a gun like that.’’ He scrambled around looking for it. ‘‘Well, that pisses me off.’’ As he searched, he spotted a ball-point pen that should not have been floating freely. ‘‘I’ve looked everywhere over here for that Hasselblad, and I just don’t see it.’’

‘‘It’s too late for sunrise, anyway,’’ Armstrong lamented.

‘‘You want to get it before TLI,’’ Aldrin noted, referring to the camera. Objects floating freely would have to be collected and stowed prior to the manoeuvre, to prevent them slamming into something else and causing damage.

‘‘I know,’’ agreed Collins. As he continued his search, he endeavoured to avoid making movements that might induce ‘space sickness’. ‘‘Ah! Here it is, floating in the aft bulkhead.’’ He belatedly snapped a few pictures of sunrise.

‘‘How are we doing checklist-wise?’’ Armstrong prompted, several minutes later. ‘‘Let’s make sure we don’t screw up and forget something.’’

‘‘After I extend the docking probe,’’ Collins replied, ‘‘I have got to copy down a bunch of data, and you’ve got the RCS hot-fire.’’

As they approached Baja California, McCandless called via the relay station at Guaymas in Mexico to remind them that they were coming up on Goldstone, but the vehicle barely rose above Goldstone’s horizon and the station received less than 1 minute’s worth of the FM carrier signal without any image modulation. While this proved that the transmitter worked, it had yet to be demonstrated that the camera functioned. One point of progress, however, was that Collins decided that having the monitor float beside the camera was awkward, and that in future it should be taped on top of the camera.

Houston monitored the spacecraft’s telemetry to verify that the docking probe extended properly, and that the RCS thrusters in the quads positioned at 90-degree intervals around the service module imparted pitch, yaw and roll impulses – using only small ‘blips’ in order not to disturb the S-IVB. The Instrument Unit was then updated by direct uplink with the parameters of its orbit and the time and duration of the TLI manoeuvre. This data, plus information on options for an abort if that burn did not go to plan, was also read up to Collins, who wrote it on the flight plan and read it back for confirmation. It had once been intended that there should be a teleprinter to simplify the provision of such information, but this had been deleted in an effort to control the mass of the spacecraft. Because Goldstone had not been able to verify the television camera, as they passed over Florida they transmitted to the Merritt Island Launch Area where, although there was no longer any apparatus to process an image, it was possible to confirm that the carrier signal was modulated. McCandless reported via Canary Island on revolution 2 that the telemetry from the hot-firing indicated that one of the RCS quads was cold. On checking, Armstrong reported that the switch for the heater in that unit had been set incorrectly. ‘‘It was Off; it’s On now. Thank you.’’ With the heater operating, the unit rapidly warmed

up.

As Apollo 11 approached Earth’s shadow for the second time, Collins resumed his couch and they put their helmets and gloves back on in preparation for the TLI burn. McCandless attempted to call through Tananarive but received no response; it transpired that the remote station was not uplinking. Unconcerned, the astronauts worked on through the checklist.