Category Archives: Ground stations

DIY Space: DIY Satellite Ground Station

Yes, ground station charts typically look very boring. Nature of the beast, I’m afraid. Image from SatNOGS.org.

Anyone who has been following this site knows that satellites are in many different roles, accomplishing many things beneficial to humanity.  But none this really matters without a way to communicate with them.  If a satellite takes a picture, how does that picture make its way to Earth?  If a satellite requires an element set update (an update of a satellite’s orbital track) or troubleshooting, how does that occur?  To communicate with satellites, to get the data they acquired back to Earth, you need ground stations.

If you are more ambitious, or have a lot of satellites to be communicated with, then you have a ground system.  This site has talked about both in the “Imaging Satellite Operations” series, starting here.  Typically these ground stations and systems cost a lot of money, but there’s a group of folks out there trying to make ground stations more accessible using open-source tech. The group, calling themselves SatNOGS, is trying to make it easier and more affordable for folks to become part of a (according to this Hackaday.com post) “Near Space Network.”

So, yes, you now have the opportunity and plans available to create your own satellite communications ground station.  Plans?  Yep, SatNOGS actually has a recipe to help you talk with satellites, and you can go to this part of their site to see what parts you need to do so.  Software is also available, including software defined radio (based on GNURadio–pretty nifty software, actually–you can use it to monitor A LOT of different frequencies) and SatNOGS’ own tracking and contact scheduling software.  By the way, GNURadio is also used to talk with the ISEE-3 satellite.

If you have your own ideas about bettering ground stations and systems to contribute to SatNOGS, first you should admit you’re a space nerd.  Seriously, confront this and then be comfortable with it.  But second, if you do have ideas, the SatNOGS fellas seem friendly enough and are encouraging all types of space enthusiasts to contribute to the ground station’s design.

Build your own, or contribute to SatNOGS; either way, you too, might be able to command a satellite–or at the very least get some satellite data.

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Providing Information Equality with Satellites

Outernet’s prototype portable satellite receiver dish terminal. Image from Outernet.

Outernet is proposing to broadcast information, via satellite, to portable base stations that are also wireless networks.  The wireless networks would be free and open to the very poor around the world.  Outernet wants to provide information equality to those poor people.

They mean well, I suppose.  And it’s a very interesting idea they’re pursuing with some simple but well-made hardware.  The hardware and idea, both developed by Outernet, seem to address a problem that maybe we in the “first” world see, but maybe someone who is just looking for a non-lethal drink of water or fighting for a meal may not even want.  It’s that whole “heirarchy of needs” thing that Outernet might be pushing against.

The idea and devices were developed by Outernet, who have designed a very portable satellite receiver dish.  Using existing terminals, Outernet would initially uplink their data to existing geosynchronous (GEO) communication satellites.  Eventually, Outernet proposes they’ll have their own ground system that will send data to cheaper low earth orbiting (LEO) cubesats that will then send information down to the receiver dish.

The dish would receive signals from a satellite.  The signal loops, sending the same data over and over.  The data within those signals has already been prepackaged in a way to be efficiently transmitted.  The satellite receiver dish would receive the transmitted data, and save it.  The data itself would be a “collection of the greatest works of humanity, as decided by humanity.” The collection resides on a storage drive in the receive dish, on a local wireless network, to be accessed by locals whenever they are in range.  The core of the collection would be all of Wikipedia, Project Gutenberg, open courseware, and works Outernet dubs as critical–all broadcast in various languages.  The information would always be updated, but it wouldn’t be a “real” internet connection, since no signal is generated from the satellite dish to the satellite.  And the presentation to the viewer wouldn’t be quite like what you or I are used to on the internet, due to data bandwidth constraints.

But, according to this Wired post, Outernet say they aren’t trying to solve an internet connectivity problem.  Rather, they are trying to resolve an information deficit/equality problem, and resolving that problem doesn’t necessarily require a two-way data connection, at least to the satellite.  This might work, but I do wonder if their identified customers will really appreciate this.

The internet is a good thing.  It’s helped to make things cheaper, provides access to knowledge, allows ideas to mingle, etc.  We recognize this in the US.  But here in the US even the poor have cable TV, access to cheap food, etc.  (although, I see a lot of homeless out there–and if my job situation keeps deteriorating, I may be joining them).  Access to banks, social and health nets, employment portals, have a network component to them now.  We all see the necessary as something useful, fun, interesting, and more.  So something like this might make sense to us.

But in areas where there are more fundamental survival issues, this may not be viewed as necessary at all.  Would a concept like information equality even make sense in that kind of scenario?  I guess we will find out by watching Outernet.  You can follow them by going to their site and reading their blog.  And people don’t have to buy their equipment.  They actually show some DIY instructions, based on a Raspberry Pi.

I wish them luck and I hope they do succeed in this endeavor.  If they’re right, maybe there is a thirst for more than the basics out there.  If you’re interested in following them, just go to their blog, here.

Image from Outernet.

ISEE-3 Reboot Project: Critical Communications

Image linked to ISEE-3 Reboot Project Page.

In spite of all obstacles, including equipment age, the International Sun/Earth Explorer 3 (ISEE-3) is talking to people on Earth again.  Not only is it talking, but the people sending and receiving ISEE-3’s messages are volunteers for the ISEE-3 Reboot Project instead of paid Federal Government employees.  All people involved with the project are working towards a vision of using ISEE-3 once again.  ISEE-3 is a satellite originally sent out by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) to study the events that occur when the sun’s solar wind interacts with the Earth’s magnetic field.

The ISEE-3 mission was launched in 1978.  For those people that remember and who lived in that decade, computers and communications weren’t near as sophisticated back then as they are now.  Back then, Mattel’s “Football,” an electronic game using LED dashes representing the football and players, was considered pretty fancy (I was so happy to get one for my birthday).  The “Speak & Spell” debuted in 1978 (how would ET ever have gotten home without one?).  The Commodore PET, Apple II, and Radio Shack TRS-80 were some of the big names in computing during 1978 (a person could max out the Apple II’s RAM with 48k).

Does anyone remember this game?  Image linked from the Handheld Museum.

So, even if ISEE-3 was launched with more sophisticated electronics than those, the electronics weren’t likely that much more sophisticated.  There apparently isn’t even a computer on board the satellite.  Imagine the kind of scrounging going on today for the specialized communications equipment, and more importantly, the detailed knowledge required to operate an old spacecraft like the ISEE-3.

How do you even figure out how to “talk” to an old satellite?  This post from John Malsbury’s site tells that story (hint:  it gets a little technical).  Of course, instead of a computer that took up a room, the volunteer engineers are using laptop computers (probably while playing Minecraft at the same time).

The upshot of it all is, as of June 3rd, 2014, the new ISEE-3 team is sending to and receiving commands from ISEE-3.  The team is using the Arecibo Observatory to communicate with ISEE-3.  They’ve determined all 14 of satellite’s the payloads are still working.  If you’re at all curious about the original experiments each payload did, go to this site.

The ISEE-3 Reboot Project is initially planning to just move ISEE-3 into another orbit–one which is “gravitationally stable,” nearly 930,000 miles from Earth.  In a way, the Reboot Project is “parking” the satellite.  But to get there, a series of maneuvers need to happen, including flying past the moon at an altitude of only 50 kilometers above the surface.  Which is why the communications part is really important.

Why all this activity?  Simple, this way it’s mission can be “rebooted” and the ISEE-3 will be ready for the next comet chase.

Jam On It!–Arabsat’s Ethiopian Space Jam Problem

You knew this was the picture I was going to use. It’s only right, right? Image linked from Gifsoup, but Mel Brooks and his Spaceballs crew created it.

What does a satellite operator do if someone jams its broadcast signal?  Specifically, what does Arabsat do when someone jams its TV signals in Africa and the Middle East?  According to this Satellite Today post, the company first finds out where this “intentional uplink interference” is coming from.  Then it takes its case to the International Telecommunication Union (ITU) and, in this case, the Arab League.

Arabsat provides telecommunications and television broadcasting through its geosynchronous (GEO) satellites throughout the Middle East and North Africa.  According to Arabsat’s research, the jamming seems to be originating from Ethiopia.  That’s right–someone in Ethiopa has been jamming particular satellite TV signals last week.  RFI, France 24, Deutsche Welle, Al-Jazeera Arabic, Voice of America, and BBC are some of the jammed channels.

Why is Arabsat going to the ITU?  An arm of the ITU is the cooperative organization responsible for allocating “global radio spectrum and satellite orbits.”  It is the organization that is concerned about coordinating radio spectrum use globally.  Nations and private organizations coordinate the satellite radio frequencies they use through the ITU.  This is to help minimize the number of radio frequency conflicts between those organizations.

The ITU also  coordinates and allocates orbital “slots” for nations and private organizations to use.  For Arabsat, the GEO slot is 26 degrees east of the Prime Meridian.  Because the jamming seems to be affecting not just Arabsat communications, but the satellites around the 26 degrees east slot, the ITU is the natural place for anyone with a grievance and problem related to satellite communications.

Coverage of Arabsat. Image linked from CDN Satellite Today. Click on link to embiggen.

What happens if they actually catch the Ethiopian jammer?  According to this BroadbandTVNews.com story, Arabsat will:

“…follow up the matter and take all appropriate actions to prosecute the culprit at the judicial authorities and the international organisation of frequencies and any legal means that may deem appropriate to ensure that any damage already incurred or to be incurred by the noise, will not go without legal action, regardless of whether this damage is direct or indirect.”

Maybe a more civilized option than using a cruise missile or drone to solve the problem?  After all, a jammer being used in wartime just becomes a priority target on a list.  But this isn’t wartime, and making something expensive to do, such as operating a jammer and then being fined and/or put in jail, is probably an excellent deterrent.

This does show one of the drawbacks of satellites.  Jamming a satellite’s up/downlink and broadcast signal causes all sorts of problems for operators and users.  Operators lose the ability to command a satellite, and of course the broadcast signal from the satellite is overcome with the radio “noise” a jammer creates.  Sometimes it might happen and an operator might not even know about it.  Arabsat notes this occurred to one of their satellites back in 2012 as well.

Why Space Matters: HEO Satellite Operations, Part 4–Moley, Moley, Moley, Molniya!

During the last lesson, you might have been enlightened with the information that even though the Soviets have used, and Russians do use, geosynchronous (GEO) orbits for satellites, they seem to have a special place in their vodka-filled hearts for the highly elliptical orbit (HEO).  And that last lesson enumerates the reasons why they like it.  For one particular instance and for one particular HEO, they liked it so much, they gave the orbit a name.

Soviet satellite scientists were very clever when they first started using the HEO.  They already knew the Earth’s squashed pumpkin shape (its oblateness) normally “spins” (or perturbs) a satellite’s orbit slowly about the Earth’s axis.  But, they somehow figured out that a HEO satellite with a 12-hour orbital period using a specific inclination of 63.4 degrees nearly nullified that perturbation.  That particular period and inclination is a special kind of HEO the Soviets named “Molniya.”  By the way, they named their communications satellites in this orbit AND a rocket (a modified R-7), Molniya, too (so no potential for confusion there, I guess).

The Molniya orbit. Image from Wikipedia–click on it–you know you want to…

Let’s translate all that scientific “hoo-haw” into English a little bit.  The angle between the path of the satellite’s orbit, as it passes from south to north over the Earth’s equator, and the Earth’s equator itself is 63.4 degrees.  The satellite’s particular HEO is a 12-hour long trip around the Earth, which means the Molniya satellite orbits the Earth twice a day.  And the inclination was specifically chosen by Soviet scientists because it’s a very stable orbit.  The satellite seems to be rising, flying over the Earth, and setting at about the same spots over the globe every single orbit (there’s a slight shift backwards around the Earth of about -.07 degrees per orbit).  These characteristics are very specific to a Molniya orbit.

But the best thing about the Molniya is when a satellite in that orbit is near and at the Molniya’s apogee.  The satellite appears to “hover” over the Earth (no mystery why—read this lesson for a refresher).  Of a 12-hour period, there’s nearly 8-9 hours of time when the satellite can “see” most of a particular part of the northern hemisphere.  This characteristic means that for about 8-9 hours, the HEO/Molniya satellite can maintain contact with a ground station, broadcasting messages from that ground station to all receivers within that satellite’s Field Of Regard (FOR), which includes areas above 70 degrees north latitude.  Below are a few Wikipedia-cribbed pictures showing a satellite’s FOR in a Molniya orbit four hours before apogee, at apogee, and four hours after apogee.  As you can see, there’s a lot of the Earth in view during all that time (Russia, China, India, Koreas, etc.).

View of Earth four hours before apogee in a Molniya orbit. Image from Wikipedia–click to embiggen.

View at apogee in a Molniya orbt. Image from Wikipedia–click to embiggen.

View of Earth four hours after apogee in Molniya orbit. Image from Wikipedia–click to embiggen.

There’s one obvious problem for people wanting to broadcast 24 hours a day with a Molniya satellite:  communications only lasts about 8-9 hours from a Molniya satellite’s “rise” to its “set” on the opposite side of the Earth.  This means there is “dead air” for their broadcast area for nearly 15-16 hours each day.  Yes, 15-16 hours—a broadcaster’s nightmare (unless they’re union).  The gap is because the Earth has continued rotating, and by the time the Molniya satellite rises again for the second orbit of the day, the other side of the planet is now in the satellite’s FOR.

There is an answer to this problem, though.  If 1 or 2 more satellites are put into different Molniya orbits, ones in opposing orbits (so the orbits create an “open scissors” if you traced their paths—see below), then the broadcast coverage is 24 hours.  And this is what the Soviets did, successfully starting the Molniya constellation by launching the Molniya-1 satellite in 1965 (after two satellites had been destroyed in previous launch attempts).  And even as the Soviet empire fell, the Russians used and continue to use the Molniya orbit today.

Moley 1

The upshot of the Molniya orbit is that it’s an orbit perfectly suited to help a communications satellite (or satellites with other missions) keep sight of countries at very high latitudes.  Using multiple satellites in a Molniya orbit provides a very good, very big, FOR and can be extremely useful for communications, especially with stations and vehicles working within the Arctic Circle.

But what are some of the other things being done with satellites in HEO?  Maybe Part 5 of this HEO Series will answer that question.