Receiving Dead Satellites with the RTL-SDR | Hacker News Reader

Receiving Dead Satellites with the RTL-SDR

rtl-sdr.com

162 pointspavel_lishin54 comments

hey i did my senior undergraduate thesis on orbital debris removal and mitigation. specifically on mitigating the effects of the Kessler Syndrome.

..and it's a lot harder than just shooting another satellite up to bring the old one down. you have to match not only the speed of the target satellite, but the altitude and orbit it's in too.

once you've done that, you can't just attach to it, fire off thrusters and deorbit it; Newton's law still applies. You'll bump into it and according to the 3rd law the target will apply an equal and opposite force. you can't shoot it with a harpoon cause that'll cause more debris.

but let's say you do attach to it somehow or utilize something like electrodynamic tethers (which is what the Japanese Space Agency, JAXA) is using. you can't just throw it back to earth and hope the atmosphere does the rest; you have components that may not completely break up and may rain down upon populated areas(c1).

usually once a target satellite is acquired, it is moved to a graveyard orbit away from operational satellites.

i was going to submit an application to YC to startup a space company dedicated to space debris mitigation but it seemed a bit too complex.

(c1)-This is why most of our spaceflight launch locations (Cape Canaveral, Vandenburg, Wallops) are on the coasts; they fire away from CONUS so just in case there is a catastrophic failure, the debris doesnt rain down on your house.

If you're interested in pursuing the idea of a (YC) startup on the topic still, feel free to drop me a line. See [1] for a bit of background on me. Active Debris Removal as a service (ADRAAS?) is going to be HOT. I know a few companies in the space already, and there are plenty of problems to address.

[1] https://news.ycombinator.com/item?id=8573800

Hey yea definitely! Is there a email/FB or other contact point I can communicate with you on?

"ADRAAS" haha I love it. I prefer to call it ODRAAS though (orbital debris removal as a service) to distinguish the 'orbital-ness' of the debris haha.

ODRAAS works too :) My email is in my profile.

It's not. You have to explicitly put contact info in your about section if you want it to be visible to anyone except the YC admins.

Ah, didn't realise that it's only admins that can see that. Thanks for the tip.

i don't see an email

strange, I filled it in. Anyway, you can reach me at me@ + my username + .com

High-Yield Debris Removal As A Service:

H.Y.D.R.A.A.S.

Nice! :)

Maybe lawmakers could help by mandating that if you launch a kg you have to deorbit a kg. Given the right incentives I'm sure the private market can solve this problem.

Yep exactly. It's already happening. I have a few colleagues that are knee-deep in space law and it's interesting to see how rapidly the landscape is changing in response to the growing threat to essential space-based assets (weather satellites, GNSS (GPS, Galileo), disaster-monitoring satellites etc.).

At the moment it seems like letting the atmosphere burn up debris is the usual procedure, but I wonder how much longer that can be sustained without any significant effects on the atmosphere - it's a somewhat similar concern that stopped us from dumping waste into the ocean and limited the burning of things at ground level and letting the smoke dissipate into the atmosphere. Thus, even if we could somehow deorbit all the current debris and let them burn in the atmosphere, it might not solve all the problems.

For those of you interested in orbital debris, there is a newsletter put out by NASA on the subject worth subscribing to. It's a free quarterly PDF.

http://orbitaldebris.jsc.nasa.gov/newsletter/newsletter.html

> An audio example of Transit is over here https://dl.dropboxusercontent.com/u/124465398/Transit5b_5_20... (my recording) it sounds like some kind of melody song.

This is in fact quite incredible to listen to. There seems to be a lot of "character" encoded in it. It goes through long and slow periods, parts with rapid notes, etc. Definitely worth a listen and pondering what kind of data it's "talking" about.

> There are many shutdown Satellite’s who apparently having a life of their own varying from Military, Navigation, Experimental, Weather, and also Amateur ones.

Wait, there are amateur satellites?

Hahah, will they fall in our heads some day?

My interpretation is that there are amateurs who hack into these shutdown sattelites that come back to activity.

Yes, there are, most of them are from universities, like this one: http://www.tudelft.nl/en/current/latest-news/article/detail/... Also some hard-core HAM operator clubs are known to have launched their own amateur satellites

There's actually a whole organization dedicated to launched amateur radio satellites: http://www.amsat.org/

My Alma Mater :) There are A LOT of university small-sats out there now, and I know at least a dozen teams personally. University-based satellites provide a fantastic educational tool for students, so they'll also be a (small) part of the landscape.

Yes, starting in 1961: http://en.wikipedia.org/wiki/OSCAR#OSCAR_1

For a very active organization, check out http://www.amsat.org/

Much of modern satellite comm technology came from amateur radio experiments. Have you heard of OSCAR:

http://en.wikipedia.org/wiki/OSCAR

"Throughout the years OSCAR satellites have helped make breakthroughs in the science of satellite communications.... Most of the components for OSCAR 10 were "off the shelf" and tested by group members. Jan King led the project. Solar cells were bought in batches of 10 or 20 from Radio Shack..."

Also, OSCAR 1 was just four years after Sputnik (the first artificial earth satellite). Many Ham radio enthusiasts, from all over the world, are hard-core engineers.

If you're interested, some friends of mine at work launched one last year http://funcube.org.uk/

Transit 5B-5, one of the two very early satellites mentioned, seems to have carried a very early RTG.

I wonder if it is still running on its nuclear power.

For those that were wondering:

> Radioisotope Thermoelectric Generators, or RTGs, provide electrical power for spacecraft by converting the heat generated by the decay of plutonium-238 (Pu-238) fuel into electricity using devices called thermocouples. Since they have no moving parts that can fail or wear out, RTGs have historically been viewed as a highly reliable power option. Thermocouples have been used in RTGs for a total combined time of over 300 years, and a not a single thermocouple has ever ceased producing power.

Source: https://solarsystem.nasa.gov/rps/rtg.cfm

I had to look it up as well. I am amazed that voyager 1 is running on about 470 watts of power and is still able to transmit an intelligible signal to earth. Im also wondering how much a transmitter that was capable of the Ghz range cost back in the mid 70s when it was built. Incredible stuff.

GHz transmission in the 1970s is not special. The cavity magnetron was invented during WWII and used for RADAR purposes and not long after microwave connections were being used for long distance telephone connections.

The magnetron is a good point! But for RADAR applications you just need a big source of emissions that can be pulsed on and off. The magnetron does that well enough. I have never heard of anyone using a magnetron modulated in some scheme to transfer information at any some useful rate. It's definitely possible with gunnplexers. You could certainly do more code with a magnetron, but even that would be difficult given their unstable output frequency.

The transmitter uses only 22 watts. A cell phone is about 2 watts. It's striking how little it takes.

The choice of antenna is a lot more important than transmit power. Especially for an application like this where high-gain is needed.

It also helps to be in space, where there's nothing to obstruct your signal. Barring obstructions, radio waves propagate indefinitely.

There's still inverse square law at play, although it's much more forgiving than atmospheric attenuation (logarithmic db loss with distance versus linear).

Microwave towers were pretty common in the 70s, and were used before then for long distance telephone links. I can't imagine that they were all that more pricey than any other transmitter.

As for signal transmission, consider that the radio noise is 100 times stronger than the GPS signal your phone's nav software is trying to decipher. Now imagine a humongous antenna with much more processing power than your Samsung Galaxy. Though amazing that we can still make sense of Voyager's signals, it's not quite to the "miraculous" category.

The two Voyagers are often seen downloading data through NASA's Deep Space Network. Here's a real time DSN status page: http://eyes.nasa.gov/dsn/dsn.html

What a neat website! Anyone who is reading down the comments and hasn't checked it out, you should!

Thank you. I knew about the DSN but didn't know there was a status page. Quite fun.

That's pretty amazing. I am guessing that this wins the reliability vs power tradeoff. I wonder how much more efficient a more traditional system is vs an RTG.

5B-5, specifically, is not powered by an RNG, however other satellites in the same series were[1]

[1] - Satellites By Michel Capderou, pg 214

So I know there are some initiatives and even a Swiss company that wants to clean up our space junk. Has there been any thing written(and Im sure there has, Im curious to read it) about when we will hit a tipping point that it becomes dangerous to even launch into space?

Not a time prediction, but check out the Kessler Syndrome:

http://en.m.wikipedia.org/wiki/Kessler_syndrome

"collisions between objects could cause a cascade—each collision generating space debris which increases the likelihood of further collisions."

If this happens, the astronauts/cosmonauts will need to jetpack to a neighboring station to escape the debris storm and return safely to earth using a Soyuz capsule.

(reference to the plot of "Gravity")

There are a lot of papers that have been written on the topic, dating back all the way to Kessler and Cour-Palais [1]. There's a recent NASA technical report that catalogs a lot of the work that is being done on debris population studies that's worth glancing at [2].

I'm involved in the European Stardust network [3] and am working on remediation technologies for space debris. There are some particular candidates for active removal that we know pose a great risk. One of the highest-risk objects is Envisat [4]. There's a concerted effort in Europe through the Clean Space Initiative and the e.Deorbit mission in particular to figure out how to remove large, dead satellites like Envisat [5].

For the last six months, I've been working on building a model for preliminary design of missions that could potentially target multiple debris objects in one shot [6][7]. Turns out that it might be more cost-effective to design multi-target debris missions (paper will be o arXiV by the end of the year).

As of next month, I'm going to be leading a new project called Scarab that'll last 12 months. I'm going to be working with a team to develop an end-to-end simulator for the removal of dead rocket bodies (e.g., Ariane) that pose a significant risk to operational satellites, focussing on robust Guidance, Navigation & Control for proximity operations.

So yea, there's a lot of work being done in the field and there's a general consensus that we need to act now to subvert the doom scenario of an uncontrollable collisional cascade that will most definitely render vital orbital bands useless.

[1] http://onlinelibrary.wiley.com/doi/10.1029/JA083iA06p02637/a... (paywall)

[2] http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2014000...

[3] http://www.stardust2013.eu

[4] https://earth.esa.int/web/guest/missions/esa-operational-eo-...

[5] http://www.esa.int/Our_Activities/Space_Engineering/Clean_Sp...

[6] https://github.com/kartikkumar/atom

[7] https://github.com/kartikkumar/d2d

there's definitely a need to reduce and mitigate orbital debris, but the monetization is polarized to NASA, ESA, SpaceX, and possibly Bigelow Aerospace when they get their structures operational and I think YC will want something that's not restricted to a few agencies and space companies. I'm jus tthikning out loud however

Not entirely. Space law is moving pretty fast at the moment, so I think it's safe to say that commercial ventures that launch satellites will be required to guarantee safe de-orbiting in some fashion. There are significant monies in Europe at the moment through ESA and the EU, but I'm convinced that new money streams will open up within the coming 5 years. The public funding opportunities also provide some sort of a basis for a business model centered on providing active removal services. I'm going to be at the CODER workshop in a couple of weeks at University of Maryland to present my work, and there are a number of companies that are going to be present too [1]. One of the panels will specifically address "entrepreneurial opportunities" (Panel 7).

[1] http://www.coder.umd.edu/workshop/program

This chip -- designed as a digital TV radio receiver -- is truly fantastic. So is the story behind it's instruction set "discovery."

Could you link to the story about the discovery of its instruction set? That sounds really interesting but I can't find it.

I'm not sure where I learnt of it now, but here's what I believe to be the email that started it all: http://thread.gmane.org/gmane.linux.drivers.video-winput-inf...

If I remember it correctly, Realtek made this board as something to market as capable of receiving public digital TV waves. It was widely manufactured, likely as part of the big U.S. digital switchover, so volume was high and costs accordingly low, saving passed on to the consumer in the form of cheap hardware. As far specs, using for "just" digital TV was like putting a Ferrari engine in a Prius. But it lay mostly dormant because the chip's API wasn't published except to the handful of vendors who likely paid millions for the spec.

But curiously sniffing around the simple device, in true hacker style, someone found traces of something far more awesome and dashed off the above email to a public mailing list. From there, the a community of software radio enthusiasts together reverse engineered enough of the API to make the extremely low cost (~$20) consumer hardware usable with open software such as the software defined radio (SDR) application Gnuradio. For a lot of the cooler applications of SDR you need two radios - one to transmit and another to receive - and previously the cheapest options were USRP brand radios from an outfit that did wonderful engineering but whose hardware was prohibitively priced for amateurs.

So this has occupied my thought all day- What are these signals? What "data" is being transmitted here?

Wow! Didn't realise these chips could be used for SDR.

Obligatory XKCD: http://xkcd.com/1337/

Would it be possible to have a two way conversation? Get a command line somehow?

That would so cool.

Also, what are the speeds of these signals? How long would it take to load The Pirate Bay site from a sattelite?

Badass potential.

As a satellite internet customer, I can say you're not missing a whole lot. There are indeed command frequencies for them, though. So long as they're farting all over the radio spectrum, it'd be nice to make them transmit something other then an unmodulated carrier.

Man I wonder what the plain text transmit speed would be for a sattelite.

Talk about avoiding all government censorship. lol.

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