Apollo Unified S-Band communications

Looking at the speed vs. time give location, so?

Of course due to rotation of the earth there was and still are problems at acquisition from ground stations how was/is it managed ? Has anybody seen the film named "The Dish" . I loved it . World wide cooperation in that event is ,may be, the best result. Sorry for my English I'm French BTW.

Three days after launch it was in a geocentric orbit of something like

Since some S-IVB stage escaped the Earth gravity, it must have been a heliocentric orbit at th end of the burn. .

Only during the capture by the Moon.

Initially the star navigation was intended to be the main navigation system and two way ranging was intended to be experimental.

Each station about to receive hand-off was given position and velocity data that enabled them to pre-calculate the expected Doppler shift, and pre-compensate it.

To make this easier, the transmit frequency was lowered so that it would be received by the approaching spacecraft bang-on centre frequency. As the bird flew overhead, the transmit frequency was gradually increased to stay on the centre at reception, so the spacecraft PLL didn't need budge, just keep it in phase. And obviously, before LOS (loss of signal) they would do hand-off to the next station, which would appear to be right on frequency again.

Details are in "Range Measurement as Practiced in the Deep Space Network":

It was a fun movie, but the Australian stations weren't staffed by a couple of retrained sheep farmers, but by a couple of hundred highly expert Australian staff - engineers and scientists, and the service folk; gardeners, diesel fitters, kitchen staff, etc. The movie focused on Parkes, whereas the real action mostly happened at Honeysuckle Creek. Most of the HSK staff took a pretty dim view of that. CSIRO loved it, and have lied for decades about the extent of the role of Parkes.

Clifford Heath.

Integration is fine until the errors start to add up.

These days trajectory calculations use Kalman filters, which gets the optimum multi-variate estimate from a number of multi-variate sensors (each with its own multi-dimensional error distribution).

I'm not sure if Apollo did that though - I think they precalculated the optimum path and the slope (local derivative) of all the variables along the path. Apollo 13 was a problem, because they had to recalculate a completely new trajectory.

Clifford Heath.

FWIW:

has imagery of the on-board hardware and other interesting details including the Apollo Experience Report that I've not seen before.

has other artifacts.

-- A host is a host from coast to snipped-for-privacy@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433

Nice links, thanks, I'll have to work through them.

The "Proceedings of the Apollo Unified S-Band Technical Conference" document was taken from . Colin Mackellar is the owner of the latter site and the person who scanned the original paper version to this PDF.

Clifford Heath.

Found a link that the fallback baseband voice was used for A13 to conserve power, and there was a local ocillator for the transmitter fallback.

D'oh, that should be sorry for the typo.

There was a problem retracking Skylab. There was a receivable signal, yet it was too difficult to obtain main lobe lock on spacecraft. We tried visually to aim antenna even to get some signal lobes with large and small antennas for a few days. The given predicted orbits were off, and only when NORAD finally gave fairly accurate predictions were they able to lock on. We tried the hand pointing and video feed, yet we were way off LOL.

Greg

They even had emergency "key" i.e. Morse code.

The "local oscillator" was needed anyhow - it just required manual tuning because the phase lock loop had no received phase to lock to. It was probably just the same VCO... but I suppose they could have had a crystal source to "lock" to.

Great level of technical details, very much appreciated! Thanks for sharing.

Two questions:

1. 190dB isolation?! Really needed or some unnamed genius had a boring day and went to check where the limits are?

1. 65m dishes for emergency? What kind of emergency? Just as a backup for the 9m ones or to read brain waves straight from the orbit? ;-) Those are HUGE!

Best regards, Piotr

On 16, the steerable high-gain antenna on the LEM wasn't, or rather it was steering just fine but the aiming was err sub-optimal...... [One of the motors failed.]

They were GO anyhow because Goldstone had enough margin with the BIG dish to use the LM omni antennas. And once down the Rover had a dish. Aiming it was fun. Don't recall if they also had the deployable dish that 12 & 14 used but suspect the weight was used for the rover.

Many thanks for the details and the link. A last question: Was polarization used for example to confirm the attitude of the spacecraft ?

Very nice presentation, Clifford, thanks for posting it. Just finished watching it.

You might add a link to the 'Proceedings of the Unified S-Band Technical Conference' .pdf to the video description, if it will still let you edit it:

It touches on all aspects of the Apollo program rather than just the communications hardware.

I wish Lindley at JPL had gone into more detail about how the correlators in the "Mark I" range receivers worked. Using several short PRN codes instead of one long one probably allowed for all kinds of clever analog and semi-analog tricks that wouldn't even occur to someone faced with a similar problem today. Tubes full of mercury, special CRTs with weird phosphors, that kind of thing.

There might have been limits on how much they could talk about back then, I guess. Or maybe it was so trivial as to not be worth discussing.

-- john, KE5FX

I went to school on Mark 1 but that was long ago. Also had school on the newer tone ranging machine. Mark 1 had dynamic logic, a signal or no signal. The tone ranging machine had analog, TTL, ECL, RF, a beast to work on.

Greg

I doubt it. I don't think the antenna returned polarisation signals from the magic-T hybrids. It wouldn't work when using the omni antennae, and they'd need to know the spacecraft high-gain antenna pointing angle.

Clifford Heath

Done, thanks. I do include a link to the

Touches on, yes. I read the whole thing for snippets, but some chapters had nothing useful to fit into a one-hour talk.

I thought they just used a single correlator and just swept the delay on the reception PRNG vs the transmitted one. That would lock in quickly to deep sub-bit accuracy (depending on system noise and jitter). They claim is was theoretically capable of resolving to 1m, but was practically limited to 15-20m (about 0.1 bit cycle IIRC)

Clifford Heath.