Mysteries in polar orbit – space's oldest working hardware still keeps its secrets

The oldest functional off-Earth space hardware? Well, that is a great question for those into pub quizzes, aka bar trivia. 1977's Voyagers hold some impressive records beside those golden discs, just not that one. Any guesses? Astronomers are still bouncing range-finding lasers off the reflectors left on the Moon by Apollo 11 …

[lglethal]

To throw my consipracy fuel on the fire...

I'd suggest Cosmic Rays as the cause of the re-opening circuit...

Cosmic Rays regularly hit electronics and cause things like bits to flip, switches to flip, cirucits to short, and other associated damage. (Less so now thanks to specific hardening, but that definitely wasnt on the books back then). Maybe for once, those cosmic rays hit in just the right way, to break the short circuit, and let the juice flow again...

The chances are a million to one, but you know what Pterry says - million to one chances pop up 9 times out of 10... ;)

[Mentat74]

Re: To throw my consipracy fuel on the fire...

I think it's the constant current from the solar cells that opened the short...

Everyone who knows a bit about electronics knows what happens when you send a couple of amps through a short...

[Version 1.0]

Re: To throw my consipracy fuel on the fire...

We've had so many discussions for years about the creation of alien life traveling around the universe. Now after so much more investigations our research make it seem very much harder for life to travel any further than a local solar system. Even that is so difficult for us unless our solar system revolves through another solar system in a few million years when we revolve around our own galaxy.

I think that alien life is permanent but the chances of meeting it in less than million years are so small but seeing an alien life and comparing it to our life's creation and evolution would be so fascinating!

[Martin Summers]

Re: To throw my consipracy fuel on the fire...

I'm going with the theory that alien life popped round and changed the batteries.

[herman]

Re: To throw my consipracy fuel on the fire...

The chances of anything coming from Mars is a million to one, they said.

[alain williams]

Re: To throw my consipracy fuel on the fire...

Who will they send the repair bill to ?

[Marty McFly]

Re: To throw my consipracy fuel on the fire...

The question remains... Is the Great Filter ahead of us, or is it behind us?

[collinsl]

Re: To throw my consipracy fuel on the fire...

Or are we already within it, but cannot realise it?

[Anonymous Coward]

Re: To throw my consipracy fuel on the fire...

I'm thinking micrometeoroid hitting either the battery pack or its wiring.

[John Smith 19]

Honestly

Pretty incredible.

The UK has launched several AMSAT satellites over the years. I think Warwick U has been quite heavily involved.

IIRC at least one of them used the RCA 1802. Arguably the first CMOS single chip microprocessor and (I'm not sure of this) it's default CMOS process was Silicon-On-Sapphire, so very rad-hard.*

*The most amazing part to me. The active silicon layer was 0.5 micrometres thick. This implies that a modern 700micron thick wafer 699microns of that Si is purely for structural support.

[andy the pessimist]

Re: Honestly

You can wafer probe wafers as thin as 180um. Be careful the wafer will droop. Infineon and pragmatic semiconductor can make wafers 20um thick.

I don't know if the 20um thick wafers were wafer probed with a thickness of 20um. Normal probe-card over travel is 75 to 100 um.

[John Smith 19]

"You can wafer probe wafers as thin as 180um."

Indeed. PV wafers are a very different beast, running about 180-200microns. Lots of other features to lower their cost, starting with being made from the offcuts from the chip industry (not sure if they've now had to make their own semi-grade silicon due to the volume).

[Anonymous Coward]

Re: RCA 1802

My first micro used a RCA 1802. I'm pretty sure the Silicon-On-Sapphire wasn't used for the normal chips, but they did make some for space use, so someone may have been able to get some from spares.

[Gene Cash]

Re: Honestly

One of my first bikes was a Honda 750 Sabre with a partial LCD dash... in 1986. Very fancy for the time. It had an 1802 running it, according to the factory service manual.

[John Smith 19]

" partial LCD dash...It had an 1802 running it, "

Yes there weren't that may CMOS processors around even then. And CMOS copes with wide dips and peaks on voltage.

Fast forward and the 6502 is available in CMOS at 200MHz+, along with its 16bit upgrade that Apple tried in the IIGS (?)

[fromxyzzy]

Re: " partial LCD dash...It had an 1802 running it, "

There's a great writeup on the 65816 and why it didn't really work out as a great replacement for the 6502 from earlier this year: https://www.userlandia.com/home/iigs-mhz-myth

[werdsmith]

Re: Honestly

The UK has launched several AMSAT satellites over the years. I think Warwick U has been quite heavily involved.

AMSAT UK was only involved in developing AO-73 FunCube-1, but this was mostly a Netherlands project due to the pathetic hidebound restrictive regulatory environment in the UK. Launched 2013.

University of Surrey is the main UK player.

[Doctor Syntax]

Obligatory https://xkcd.com/705/

[Ian Johnston]

Alignment was taken care of by strapping large magnets to align with the Earth's magnetic field

This is such a beautiful solution that I am in awe. There is also just a hint of Wile E. Coyote to it.

[Paul Crawford]

More so if the other side has an anvil with ACME on the side...

[Red Ted]

Photon Propeller

The photon propeller that keep it rotating so as it is evenly heated by the sun, is very ingenious too.

There are four VHF/UHF antenna that are painted black on one side and white on the other, so the difference between the absorption and reflection of the two sides imparts a rotation force on the satellite.

[Doctor Syntax]

Re: Photon Propeller

It's the Crookes' radiometer.

[Red Ted]

Re: Photon Propeller

Just to be pedantic (and I know that's uncommon around here) it is a Nichols radiometer as it is radiation pressure that provides the force.

[DJO]

Re: Photon Propeller

A Crookes radiometer needs a partial vacuum to work, the Nichols one needs a full vacuum to work. I've no idea how much atmosphere there is at that altitude, it'll be tenuous but there'll be a bit.

The Nichols one turns a pair of mirrors against a fixed point so the degree of turn indicates the radiation pressure by the amount it rotates. The Crookes one just goes round and round.

So while the environment it is working in is more like a Nichols the action of rotating the craft is closer to the Crookes device. So possibly a hybrid of the 2?

[EricB123]

Re: Photon Propeller

The one I bought from Edmund Scientific ran for 20 years, then it got lost in a move. It is likely spinning every sunny day on someone's window to this day.

[Anonymous Coward]

Re: Photon Propeller

You can still just buy them. I showed mine to a colleague who has subsequently bought one for the kids as a bit of science education.

[Ian Johnston]

Re: Photon Propeller

A Crookes radiometer rotates away from the black sides, because is driven by gas molecules speeding up when they hit the hotter side.

I have one, still with its original packaging from Proops Brothers of Tottenham Court Road. Which marks my age ...

[Anonymous Coward]

Re: Photon Propeller

.. or your hoarding tendency :).

[The Oncoming Scorn]

Re: Photon Propeller

& your hoarding tendency :).

FTFYNC.

[John Smith 19]

"Alignment was taken care of by strapping large magnets "

One of the classic tactics of the "Explorer" series.

Along with "gravity gradient," IE a long telescopic pole with a heavy sensor or other mass at the end, which points along the gravity gradient to the centre of the earth.

Also no power, no electronics, no consumables.

[Bebu sa Ware]

Re: "Alignment was taken care of by strapping large magnets "

I had a look at the pdf wondering what type of magnets they used as I didn't recall rare earth magnets were thick on the ground in '74. They were Alnico-5.

I was also thinking the solar propellers continuously applying a, albeit varying, torque should have eventually spun Oscar7 giddy. [T.dt=I.dω]

Looks like from my reading an iron bar with high hysteresis losses was used to dissipate excess rotational energy. I guess the satellite rotating in the earth's magnetic field induces eddy currents in the rod which applies an opposing (3rd law) torque and are dissipated in ohmic heating. Presumably reaching a steady state where the work done by the torque applied by the solar propellers is just equal to the heat dissipated in the iron rod.

I imagine you would need some type of damping anyway as any perturbation of the spinning satellite could lead to pronounced precession.

Really clever stuff by really clever people. Having the Lady (Fortuna) blowing on your dice also helps.

[Anonymous Coward]

Re: "Alignment was taken care of by strapping large magnets "

So the magnets were the same as guitar pickup magnets?

[Bill Gray]

Re: "Alignment was taken care of by strapping large magnets "

You are correct about the magnetic field dampening rotation. It's the reason why, when you're observing junk at night [0], the more recently expended upper stages will frequently flash, or at least vary in brightness, as they tumble. The older stuff will be more constant in brightness.

It's also the reason why the stuff in still higher orbits (geostationary and beyond) will often retain its spin; the earth's magnetic field drops off pretty sharply with distance.

[0] I will occasionally step out with binoculars to look for one thing or another in the night sky. In recent years, if it's evening and the low-earth-orbit stuff is sunlit, I can't do so for more than a minute or so without some bit of junk crossing my field of view. With the naked eye, there's usually something crossing the sky that a person with a good knowledge of the constellations will pick out right away as not belonging, i.e., a slowish-moving bit of junk.

[Irongut]

"With a 1,000 km orbit and a power budget of 12-14 watts - less than a three amp USB charger, the satellite's transmitters had to be exceptionally efficient to have any chance of being usable by ordinary radio hams with ordinary radio ham gear. "

Ordinary radio ham gear can get round the world on 1 watt, which is much further than 1,000 km.

Source? The two City & Guilds radio exams I did as a teen to get my license.

[Alumoi]

Personal record: 15W, 14.918 km, FT8 on 40m.

[hittitezombie]

pissing contest

17350km on 5W with an FT-818, 14.080MHz FT4.

[werdsmith]

Re: pissing contest

QRP is so much more fun than throwing a credit card down for a kW. I confidently assume the QSO was with a key.

[Anonymous Coward]

Yes, but not likely on VHF or UHF.

Plus, the satellite is limited on size of antenna. If you need a giant antenna tracking the satellite to use it, you're almost certainly not going to use it (and if you did, you'd only be talking to yourself).

[werdsmith]

VHF or UHF will go surprisingly far with line of sight. The higher frequencies get through earths upper atmosphere layers like ionosphere better than lower frequencies. The reason that HF signals go round the world better is because they are reflected by the upper atmosphere layers, shorter wavelengths go straight through instead of bouncing.

[Gene Cash]

Antennas

> four antennas made out of cut-up metal tape measures

I remember one of the early cubesats reusing this idea and crowing about inventing it and how it reduced weight/complexity/cost, until someone spoke up and said "ack tually...."

[John Brown (no body)]

Re: Antennas

Pah! Kids today! Always re-inventing the wheel :-)

[jake]

Re: Antennas

Why the joke icon?

It's not funny. It's sad ... in the old meaning of the word.

[herman]

Re: Antennas

As Sir Mick wrote: Doing things we used to do, they think are new.

[Gene Cash]

Sobering thought

From the end of the 50th anniversary paper:

"Then there is the situation where I wonder if I can ask Tom about that...OOPS, I forgot, he died a few years ago. More than 50% of the individuals this author has named in this paper are now gone."

[Lon24]

Re: Sobering thought

Ah, but the religious ones may be convinced they will be re-activated too.

[Anonymous Coward]

Re Polish use - more likely we put something up for them or a deception.

[Anonymous Coward]

Ahhh the glory days

When men were men, and knew how to cook up some HAM

[Andy The Hat]

Please

"a power budget of 12-14 watts - less than a three amp USB charger"

Or, to put it another way

It takes 12-14W which is less than a 15W charger

Why not use meaningful comparisons? Less power than an electric toothbrush. Less power than a car brake light. Less power than a Big Mike pleasure device on vibe setting 3 err 4 errrr errrr errr ...

[hoofie2002]

Plenty of Power

The comparison of the transmitter power to a charger is meaningless as we are talking about RF power.

Amateurs trying to operate this satellite will be using directional yagi antennas which focus the beam to an extent and since it's in low earth orbit and in the sky there are no obstructions.

You don't need a lot of power to work it; a 5W handheld with a good yagi can get through.

The pain in the backside is you need to track it across the sky as it will whizz across it in about 10-20 mins depending on the pass

[werdsmith]

Re: Plenty of Power

Circular Polarised antenna signals on Oscar 7 are better heard with helicals.

[redpawn]

Re: Plenty of Power

I talked to the Space Shuttle once with a quarter wave mag-mount antenna and 5W on VHF. They used to make regular contact with amateur radio operators.

[Orv]

There's also Transit 5B-5; it can't claim the title of oldest working satellite, because it stopped functioning shortly after launch. But it was launched in 1965 and still transmits garbled telemetry occasionally, making it the oldest satellite to still emit a signal.

The Transit system itself is fairly interesting -- it was an early, pre-GPS satellite navigation system, intended to allow Navy ships and (surfaced) submarines to re-calibrate their inertial navigation systems. It was accurate to around 20 meters if the receiver was stationary.