You Too Can See Orbiting Satellites!
(No special equipment required)

 

I live in Melbourne, Florida, which is about 35 miles south of the Kennedy Space Center and Cape Canaveral Air Force Station. We see about seven Space Shuttle launches per year, and anywhere from zero to three unmanned satellite launches on Delta, Atlas, and Titan rockets every month. If you have never seen a rocket launch, it is very impressive!! Even from this distance, a night launch will light up the sky (even before it comes over the horizon) enough to read a newspaper by, and with clear weather launches are visible as far away as Atlanta and beyond (500+ miles.) As the rocket climbs higher, the flames typically turn from a bright yellow to a bluish color as the vehicle goes into thinner atmosphere and loses the yellow-burning solid boosters, if present. For Deltas and Titans, you can see the solid rocket boosters fall off and watch them arc towards the sea. Once the launch is into the third stage, the vehicle is traveling pretty much straight away from here (no matter what direction it was launched towards) and you can see the exhaust gases spread into a broad trail in the vacuum of space. Usually at night you can see it all the way until burnout, at which point it is only about twenty degrees off the horizon (and approaching Africa!!) Shuttle launches are similar except the SRBs are a lot bigger than most solid boosters (except for the Titan-IV boosters which are almost as big) and they are more visible as they tumble to the ocean. Daytime launches are impressive too, and if you get lucky and catch one either right before sunrise or after sunset, you can see the incredibly beautiful sight of the vehicle climbing into bright sunshine against a dark sky. I wish that everyone would get a chance to see a launch, there are very few things in the world as impressive. Oh yeah, you can hear them from here too... rockets make a unique sort of low rumbling, somewhat like a distant thunderstorm but at a frequency of about 8-10 Hz, rising slightly in pitch as the vehicle climbs. If you go up to the beach at Cape Canaveral, it's all about the same except you see the actual rocket more clearly, it's louder, and the sound reaches you sooner.

Most people don't realize that after launch, you can see satellites in orbit. In fact just about anyone can go outside within 2 hours of sunset or sunrise on a fairly clear night, while it's dark, and look up to see a satellite or three. Satellites fly over most points on earth constantly and the secret of seeing them is just to look carefully. Satellites usually look just like stars, but move slowly (but very noticeably) across the sky. Satellites are usually not terribly bright, usually appearing to be about as bright as an average star. Some large reflective objects like Mir, the Hubble Space Telescope, and the Space Shuttle can be as bright as Venus. You can tell a satellite from a high-altitude airplane by the fact that satellites don't blink or have any red or green lights, or strobes, and they make no sound and leave no contrails. Occassionally you will see a satellite that flashes as it rotates in the sun, however this doesn't really look like a strobe light, rather it appears as a regular variability in brightness. These flashers may become very dim between flashes or may be fairly bright with an occasional brighter flash or period of increased brightness. All satellites will fade quickly from sight as they travel into the earth's shadow (in the evening), or they may suddenly appear as they fly from the shadow into the sunlight (in the morning).

Finding satellites is not hard at all. Binoculars can help you to confirm that they aren't airplanes, but the naked eye is by far the best way to initially locate them. Look up long enough and you're bound to see a star that you suddenly realize is moving. I have seen as few as one satellite in an evening, once I saw ten over one evening and the following morning, and once at an R/C plane night-fly a group of people in a dark location all looking up at an especially clear summertime sky managed to find 17 over a couple of hours! It's amazing to think you can actually see things that may be little bigger than a television set flying tens of thousands of miles per hour which are hundreds of miles away, just by looking up.

Satellites may travel north or south, or east, or somewhere in between. It is very rare for a satellite to travel towards the west, as virtually all satellites launched into non-polar orbits are launched towards the east to take advantage of the boost provided by the earth's rotation towards the east. While the path through space describes some type of ellipse on a flat plane, the earth rotates underneath the orbit and so the path along the ground appears to be curved. Because of this effect, some satellites appear to curve slightly while visible, and the point along the orbit at which you are able to see it will determine the apparent direction you see. This is most noticeable in satellites that don't have a polar orbit. As I live 35 miles south of Cape Canaveral (28.5 degrees north latitude) a lot of satellites at this latitude are seen going almost directly towards the east as this forms the high point of many satellite's inclination (that earth-boosted launch effect coming into play here again.) In addition, people near this latitude often get three consecutive shots at seeing a satellite on succeeding orbits... once heading northeast (visible in the southeastern sky), once nearly directly overhead heading close to easterly, and once as it heads back down south and is visible in the southwest. The exact period between orbits depends on the satellite's altitude, and even though the satellite is there it is not actually visible except under the right conditions... which do not last long enough to see more than one (rarely two) passes. However it is a useful fact when there is a satellite that you can monitor or talk to via radio.

Now before you read the rest of this page, one word of warning...

I wrote this based on my own experiences, however I have not been very active with ham radio for a while, let alone with SAREX. Some of this information is certainly now outdated, such as the frequencies currently being used or the current versions of the tracking software in use nowadays. I am posting this as a general overview, NOT intending for it to be seen as the latest and greatest information. If you are interested, great, but please go to other websites that deal more directly with this (NASA, ARRL, SAREX, etc.) for more detailed and current specific information before you try to actually do it. If I get back into it, I will update this with newer info (oh to have unlimited money and time...) However, I hope that this will give you a rough idea of what it's all about. Now we've said that, so onto the good stuff.



Orbital Tracking 101

INSTRUCTOR: M. Whaley, B.S.HAM, Qr.Z
CREDIT: Not enough
TIME: All hours of the day and night
REQUIRED TEXT: FCC Rules, Part 97



There are many good tracking programs out there that provide graphical output and will show you things like the ground track and the azimuth/elevation of an orbiting object as seen from a specified location. (Anyone who has ever seen NASA Select will know the kind of output I am talking about.) I have a little Tandy 1000 TL/2 286 with CGA and running at only 8 MHz, with no math co-processor, and I run TrakSat 2.80 with few problems. AMSAT sells an excellent program called InstantTrak (the proceeds of which help to support AMSAT and amateur radio satellite projects) which is very user-friendly, oriented towards ham radio use, and will even tell you obscure little towns that the satellite is currently flying over! I recommend supporting AMSAT if you are interested in amateur satellites, for more information on satellites or the organization you can find it on the AMSAT Homepage.

Other well-known programs (usually shareware) are STS Orbit (and STS Orbit Plus), SatTrak, and QuickTrak. All of these are usually available through FTP or on BBS's with ham radio or space sections. There are a few programs out there that are specifically aimed at visual satellite spotting, but many now are meant for the amateur radio market and include features such as line-of-sight modes and can tell you when two or more locations are simultaneously within range of one satellite (in addition to visual spotting features.) Most programs use data sets called Keplerian (or two-line) elements which tell it how to predict the object's path. For the Shuttle, these need to be updated every day (due to the frequent maneuvering) but for Mir, they usually are good for at least a couple of weeks with reasonable accuracy. A good place to get these two-line element sets (readable by most programs) is to FTP to the Air Force Institute of Technology server at:

ftp archive.afit.af.mil in the pub/space/ directory.

Use anonymous as your logon name and use your e-mail address for the password. Look for files named *.tle: mir.tle, amateur.tle, sts.tle, etc.



General tips for working or listening to satellites

Once you have a tracking program, how do you use the information?? Most programs will output a file of upcoming passes that will look something like this (this is excerpted from a TrakSat 2.80 file):

                        Tracking Station: MELBOURNE,FL 
                        [ Line Of Sight (LOS) Visibility ] 
                        Input File:  MAY2795.TLE 

 Satellite  UTC     Time     Local   Time      Azimuth  Max  Min    Duration
            Date    HR:MN:SC Date    HR:MN:SC           Ele  Range  HR:MN:SC

 AO-10      03Jun95 03:09:02 02Jun95 23:09:02  S  TO E    8   8170  10:26:02 
            04Jun95 02:26:42 03Jun95 22:26:42  S  TO E    4   8221  10:13:42 
            03Jun95 18:48:18 03Jun95 14:48:18  SW TO N   13   2450  00:13:18 
 Mir        03Jun95 05:01:14 03Jun95 01:01:14  SW TO NE  40    574  00:09:14 
            03Jun95 06:38:24 03Jun95 02:38:24  W  TO N   12   1285  00:08:24 
            03Jun95 11:36:11 03Jun95 07:36:11  N  TO NE   1   2161  00:02:11 
            03Jun95 13:09:58 03Jun95 09:09:58  NW TO E   21    928  00:09:58
            03Jun95 14:46:17 03Jun95 10:46:17  NW TO S   19    980  00:09:17

For the uninitiated, UTC means Coordinated Universal Time (yeah, I know that should be CUT but they took the acronym from the equivalent French term.) Azimuth is the compass direction in which the maximum elevation above the horizon (Max Ele) will occur (usually the center point of the pass), Min Range is the minimum distance (in kilometers) the satellite is from you (this occurs very near the point of maximum elevation), and Duration is how long the pass will last from the time the satellite comes above the horizon to the time it goes back below it. The low earth orbit satellites move slowest (as seen from the ground) when they are near the horizon, and they move more quickly as they get nearer to you and thus higher in the sky, and then slow down as they set. This is not the case for all satellites, however, only those with orbits that approximate a circle and thus remain at a relatively constant altitude above the earth. Some ham satellites are in highly elliptical orbits, so they whizz quickly around the earth at perigee and go way out into space at apogee. (A stupid memory trick: perigee is the point closest to earth, and thus seems more perilous, while apogee is the point of the orbit that is farthest away.) By doing this, many amateur satellites spend most of their time either headed almost directly away from or hurtling towards the earth, and thus seem to stay in one place in the sky for hours at a time. The new AMSAT Phase 3D satellite will be in an orbit specifically chosen to minimize the relative motion of the satellite as seen from the ground, until such point as it has to go speeding around the earth so it can go back and do it again. However, we are only concerned with the low-earth satellites with people on board, so further info on those satellites will be left for the reader to track down on the related links in this document!

I have included the amateur satellite OSCAR 10 just to show the contrast in parameters between low-earth orbit and high-earth orbit satellites... note how AO-10 is visible for over 10 hours even though it is only 8 degrees above the horizon. It's orbit was picked just to allow such long communication times during a pass, and to make it easier to track for those amateurs without any automatic tracking equipment.

Now, which of these Mir passes is a good one to listen to?? Actually, they all are, depending on your equipment. When Mir is very near the horizon, say under 3 or 4 degrees, you may or may not hear it. If you have a vertical whip antenna, which concentrates its pattern in the horizontal plane, or a beam that you can point at the horizon, you will probably hear this pass, but it might be faint... you will almost surely have to turn the squelch way down to listen for it in the static noise. This obviously makes it impossible to monitor on packet until it gets high enough to break the squelch on your radio. I consider any pass over 10 degrees to be a really good one, since even at 10 degrees they are flying very close to you. Try to visualize it this way: a satellite in low earth orbit, say 200 miles high, can see from one coast of the United States to the other. Look at your location on a globe, and look at a point 200 miles away... say, the distance from Miami to Orlando. Now, visualize a spacecraft that same distance above the earth, and where it would have to be to be over the ground to be ten degrees high from your location. As you can see, it is relatively close to you, and as its elevation as seen from the ground station increases it gets relatively *very* close to you! One good thing about real-time programs is that they can provide you with information on where in the sky a satellite appears at a given moment... or you can print it out beforehand in tabular form. Since the Shuttle and Mir cross the sky so quickly, it is a good thing that antenna pointing is not always quite so critical. A whip antenna usually concentrates its pattern within 30 degrees of the horizontal - just where you will want it for the great majority of the passes! As the craft rises high enough to be outside the major lobe of the antenna pattern, it usually becomes close enough to strengthen the signal to make up for the decreased sensitivity at near-vertical elevations. In fact, your rubber ducky antenna should easily pick up Mir when it is above 10 degrees elevation.

But wait! You want to transmit to these fine folks who are whizzing merrily along through space?!! Well, here we have a problem with a whip, since you want to get as much of your signal to them as possible and the whip doesn't transmit upwards nor directionally very well! Well, the obvious solution is to use satellite antennas that are steerable in two dimensions. However, if you have those you presumably don't need to be reading this. There are a couple of other solutions. One, you could just crank up the two-meter brick and pump 200 watts through your poor little mag-mount and hope you can get through by brute force before it melts. This may or may not work, depending on a lot of variables, and many folks have talked to space stations through a vertical antenna. However, if you consider that the target you are after is a miniscule speck in one place in a great big sky, and every other direction is getting the rest of the RF energy you are putting out, it sure seems like an inefficient way to do things doesn't it?? Obviously, to maximize your chances you are going to need something directional. A beam antenna of some description will work well, since most of them have a vertical beam width that is not narrow enough to make it too hard to track the target. The method I use is to make an admittedly ugly but very cheap, handheld 3-element quad antenna out of a 1 x 2 inch wood boom, yardsticks for crossarms, and PVC pipe for a mast. (This was based loosely on a design from the ARRL Antenna Book.) I admit that I haven't talked to Mir yet, but the point is that if you want to increase your chances at any power (I only have 5 watts available from a handy-talkie) you need to do what you can to concentrate your output in the right direction. You may have heard the stories of working the Shuttle from a handy-talkie with a rubber dummy load from the bottom of a coal mine, but in reality these types of unexpected contacts are actually uncommon. Especially with SAREX, there are a lot of "big guns" out there that you are up against, and diligence is the best way to increase your odds of having this unique form of QSO! If you are willing to wait until everything is just right, and plan some ahead of time, you will be a step or five ahead of 90% of the other hams who would otherwise get to talk to them.

Now, here is the info you thought you came here for :-)



SAREX

(After you read my advice, see the link to the NASA SAREX Homepage at the end!)

FM voice uplinks on 144.91, .93, .95, .97, and .99 MHz, and packet radio uplink on 144.49 MHz. The Shuttle listens at random to these uplink frequencies, and all Shuttle transmissions are on 145.55 MHz. (ie, listen on 145.55 but DO NOT transmit there!!) The packet callsign is usually W5RRR-1 (Goddard ARC) but the voice callsign used depends on who is a ham on board the shuttle. These frequencies are subject to change depending on mission parameters... for instance, the Mir docking mission (STS-71) used 145.84 MHz for the downlink frequently and there were no packet operations. Shuttle missions are often at an inclination of about 28 degrees, which limits effective contacts to stations not too far north or south of that latitude (by not too far, I mean over a thousand miles!) but the polar-orbit missions often cover basically the entire globe. They use a handy-talkie with a cavity antenna stuck in the front window, and the chances of hearing them depend a lot on the attitude of the orbiter in relation to you. Best bet is to find out when it will be overhead, and try to watch or listen to NASA Select TV or audio on order to find out when they will possibly have some free time. Many astronauts like to talk, but even after dividing it into five different uplink frequencies, the pileup they hear is enormous at times. Please, once they start talking to somebody, be courteous and stop transmitting until you hear them call CQ. (This applies to Mir too.)



Mir

Mir is often active, and is easy to recognize because the callsign is R0MIR. They are active on FM voice and packet, and conduct all operations on 145.55 Mhz simplex. (This is the same as the SAREX downlink frequency, necessitating the oddball frequencies for STS-71 when both SAREX and Mir were on the air!) Norm Thagard, the American cosmonaut who came home on STS-71, was on the radio often around their early morning and late night (Mir is on Moscow time, so they go to bed around 5PM Eastern time) and the packet station can often be heard. (In fact, during the W4AQL SAREX attempt, we forgot to turn off the radio and packet program and came back the next day to find we had inadvertently monitored R0MIR's packet station as it flew in front of our antennas!) The Mir crew tries hard to be diligent about answering their packet mail. Mir passes last anywhere from 4 minutes for the low ones to almost 11 minutes, and occur from 4 to 6 times every day. The orbital inclination of Mir is about 52 degrees and they can see the entire US at once, so most people are in range of them, no matter where they live in the world. And since Mir can hear so many stations at once, please be considerate and wait until they call CQ before calling them! The QRM is already bad enough up there from folks who don't seem to understand that blasting a callsign into the middle of a QSO in progress is not likely to make them want to drop it just to talk to them.



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