By Michael A. Earl



     At one time, the amateur astronomer was mainly known for gazing up at the night sky with at least the naked eye, or with the help of some magnification, such as binoculars or telescopes. Today, many amateur astronomers use more sophisticated technology, such as goto telescopes and CCD cameras, to image the heavens. What some amateur astronomers may not know is that the equipment they use to take beautiful images of the night sky can also be used to take accurate photometric and/or astrometric measurements of objects of interest in the heavens.
     Many artificial satellites orbiting the Earth can easily be imaged by the amateur astronomer who owns equipment that can easily be purchased right off the shelf. While it is true that an image of an artificial satellite passing through is not as beautiful as say a spiral galaxy, the amateur astronomer can measure the satellites' positions and their brightness in order to learn more about our own satellite population that we daily take for granted.
     Amateur astronomers can now track many satellites that at one time were only accessible to those with a very large amount of money or involved in a military organization. This article attempts to explain why amateur astronomers would make excellent additions to the satellite tracking community.


     Many amateur astronomers are very dedicated people who spend many hours watching the heavens and constantly improving the designs of their observatories. They are extremely driven to push their observing capabilities to extreme levels, as if they are trying to reach a new high. This is a very commendable trait for any professional researcher. The advantage of the amateur astronomer is that he/she improves his/her knowledge of the subject right in the field. There might be people who believe that taking a few courses for a few days will make you an expert in the subject in question. My personal belief is that this is not true, especially when astronomy and satellite tracking is concerned. Furthermore, my belief is that it takes many years of practicing in the field, and not in the classroom or the office, to truly learn the fine art of satellite tracking. Although I have been involved in the subject for nearly ten years, I, in my opinion, do not consider myself a satellite tracking expert.
     Amateur astronomers learn many aspects of satellite tracking through learning about observational astronomy without even knowing it. When they learn the night sky (such as the constellations and star hopping), they become familiar with the stellar background in which the satellite population resides. When they learn how to find objects using RA/Dec or Alt/Az, they are learning about coordinate systems required to find satellites. When they use CCD cameras to perform astrometry on asteroids, comets, planets, etc., they are learning about centroiding and statistical distributions of both the images of the stars and the objects in question to achieve the highest accuracy possible, given their equipment.
     There might be some professional astronomers who would think that amateur astronomers lack the expertise, discipline, or even intelligence, to be a valid contribution within the scientific community. I would strongly disagree with such a statement. In my view, in some aspects, amateur astronomers can actually have more experience, being in the field for many hours, than a professional who may have only taken courses in a classroom. It is much like a hypothetical military situation in which the ground troops would know more about combat strategy than the commanding general who has never experienced actual combat. For the discipline, see the next section. As for intelligence, all I can say is that I have known amateur astronomers who are far more resourceful, innovative, and in some cases ingenious, than some professionals I have encountered.


     OK, many would say the next sentence is all I would need to say on this subject. The amateur astronomer is willing to stay up all night, several nights in a row, to observe the night sky. For those who are not convinced already, you try staying up for 24 hours straight (or more) and enjoy it. The subject of satellite tracking demands this type of dedication and endurance. When their own observatories are concerned, amateur astronomers are on the verge of obsession, constantly tinkering and innovating to improve their resolution, accuracy, limiting magnitude, or whatever he/she is striving for at the time. How is this aspect different from what professional researchers do? Satellite tracking demands this trait, as precision and accuracy are essential components.


     For the amateur astronomer living within a very unstable weather zone (such as southern Ontario) patience is a must. Most amateur astronomers know the feeling of missing an important astronomical event (such as a total solar or lunar eclipse, occultation of a planet, close fly-by of a comet, etc.) due to totally overcast skies (what weather forecasters might call "partly cloudy"). For the amateur astronomer, patience is learned through many years of observing. Eventually he/she will either learn to accept that weather will not always agree, or he/she will move to a more hospitable location.
     Patience is also learned through painstaking testing and equipment calibration. The art of polar alignment alone requires much patience.


     Amateur astronomers are extremely enthusiastic about the subject of amateur astronomy. To some, this might seem to be an obvious statement, but consider the reason why the last sentence is true. The main reason for this high enthusiasm is that amateur astronomers can freely observe what they want, when they want. It is doubtful that amateur astronomy would have as much appeal to most if paperwork and bureaucracy were involved. Amateur astronomers can simply point their telescopes to their objects of choice when the objects are accessible to them.
     As an example, when I began work at the Royal Military College (RMC) in 1997, I was an amateur astronomer (as I still am today). I had not seen an artificial satellite as significant before I started working there. When I began to image the objects, I discovered that satellites are extremely interesting and full of scientific value. I began to measure tumble periods, brightness, strived to increase the accuracy of the tracking data produced, and relayed information to institutions and individuals without much hassle from bureaucrats (because I did not bother with them, until I got caught that is). My point here is if the bureaucratic interference is very low, amateur astronomers can contribute greatly to the satellite tracking community because of the enthusiasm mentioned above.


     Before the CCD camera was commercially available, amateur astronomers would not have had much of a chance to track most
satellites orbiting Earth. This is simply due to the fact that good old film had way too little sensitivity to see the quickly moving and dimmer objects. The only way to compensate for this low sensitivity was to increase the aperture size of the telescope, which would have put the price of the apparatus way beyond the wallets of the amateur astronomer. Yes, it would have been possible to see the satellites through the eyepiece, but the astrometric accuracy would certainly not have been as good as it is now with the power of the CCD image.
     Before the 1990's, the goto telescope was virtually unknown in amateur astronomy. In order to track satellites effectively, the amateur astronomer would need to be able to jump from satellite to satellite efficiently without having to manually determine the satellites' positions in the sky and manually move the telescope to the predicted RA/Dec. Today, the amateur astronomer can easily jump from satellite to satellite using his/her computer console, and obtain images of satellites in order to obtain a wealth of information about the satellites' orbits, brightness, and even their status in some cases.
     Some might ask if the amateur astronomer requires a fully loaded observatory to track satellites. The answer is no. In fact, it might be more advantageous to be able to move from place to place in order to access a better view of satellites, have access to darker skies, and avoid unfavourable weather. Some would consider this mobility as an advantageous alternative to a stationary building, such as an observatory, but some would not.
     The software required to track satellites is also commercially available and quite inexpensive, and in some cases, free! Some of this software includes the ability to predict where the satellites are amongst the stellar background at any time. In fact, some CCD manufacturers are offering this astronomy software with their CCDs. Keep your eyes peeled for such deals! Some software used to perform orbit determination, given the RA/Dec positions of satellites, is available, for free, over the internet. Its accuracy, or course, is not guaranteed, but at least it is a start! Of course, there is much more sophisticated software available for all aspects of satellite tracking that are available for a price. If you have the money, you can acquire them, however, the basic expertise required for satellite tracking is still free to obtain under the night sky, right in the field, with amateur astronomy.
     Today, with an 11-inch telescope, a CCD camera, and a dark sky, the amateur astronomer can image stars to about 19th magnitude. To the ones who do not know the magnitude scale, this is about 100 times dimmer than Pluto! This is extraordinary, especially to the ones who remember barely getting Pluto on film with a 5-minute exposure! The CCD camera is truly a revolutionary tool for the amateur astronomer, so much so that the amateur astronomer can in some ways contribute to well established research institutions, such as the satellite tracking community, without having to spend an obscene amount of money.

Figure 1: A prototype for the Canadian Satellite Tracking and Orbit Research (CASTOR) research facility. Its primary goal is to determine the best accuracy that commercially available equipment can achieve, given a limited budget. In this image, the facility was tracking two Telesat satellites: Anik F1 and its newly launched twin, Anik F1-R. CASTOR comprises of a Celestron NexStar 11 GPS goto telescope, an SBIG ST-9XE CCD camera, and a run-of-the-mill laptop computer. The computer contains software for predicting satellite locations, given their orbit elements, and astrometry software. The total cost of this prototype is about $20,000 Cdn.

Figure 2: This image depicts the predicted location of the two Telesat satellites Anik F1 and Anik F1-R at 05:58:56 U.T.C. October 2, 2005. The two satellite icons are seen amongst the virtual stellar background specifically for the amateur astronomer's convenience. The software used to accomplish this is Software Bisque's TheSky Version 5. This software is very inexpensive, more so today, because of the availability of TheSky Version 6. The field of view of the CASTOR facility (13.25 by 13.25 arc-minutes) is shown as a large red square on the image. The star catalogue used is the United States Naval Observatory (USNO) A2.0. A goto telescope can easily be controlled by this software. A simple "point and click" onto one of these satellites can send the telescope to the predicted location of it, provided the telescope is suitably aligned in the usual way.


     If you are wondering this, good question! Right now, amateur astronomers are discovering and tracking asteroids, comets, discovering supernovae (both inter-galactic and extra-galactic), and discovering possible new planets in our own solar system. The question should actually be stated, "Why shouldn't amateur astronomers track satellites?". In my own view, there is a far greater practical purpose to tracking satellites than all the above combined. Our own satellite population directly serves us in the present. If anything should go wrong with an active satellite orbiting the Earth, many customers, and therefore millions of dollars, can be lost in very little time. We depend on our satellite population for our communications every single second of every single day. As far as near Earth asteroids are concerned, one MAY hit us within the next few thousand years. In my view, tracking artificial satellites to protect our valuable communications infrastructure is far more important than tracking rocks in space that MIGHT hit us.
     Some might say that the militaries of the world are doing enough to track satellites. OK, ask any one of them what their tracking accuracies are. If you were a satellite company, and you wanted a priority put on your own satellite, would any military institution take your request seriously? Now ask yourself how would an amateur astronomer reply to these questions? Because of their enthusiasm and dedication, your requests should be answered quickly, and your specific satellite should be a priority. Why? With a dedicated fleet of amateur astronomers tracking satellites, there is a vast worldwide workforce that can take on the heavy burden of satellite tracking, while at the same time being paid for their dedication (well, we can dream, right?).
     Since the subject of satellite tracking is such a new realm of astronomy, the rules of conduct have not been set in stone. Amateur astronomers can help shape this new realm such that the world can constantly keep an eye on these objects so that the satellite population can be constantly monitored.

Figure 3: A CASTOR image of the Telesat satellites Anik F1 and Anik F1-R, taken on 05:58:55.670 to 05:59:05.670 U.T.C. October 2, 2005. The bright white dots in the image are the stars required as benchmarks for precise astrometric analysis. Both satellites are known as geostationary, in which both require a sidereal day to orbit the Earth once, thereby rendering their ideal apparent positions with respect to the Earth's surface stationary. The endpoints of the satellite streaks are the subjects of astrometric analysis to determine where the satellite was (in R.A. and Dec.) at the beginning and ending times of the exposure. This image was a simple ten second exposure. North (Dec.) is at top, while East (increasing R.A.) is at left. Both satellites seem to streak because the telescope is tracking the stars (sidereal), not the satellites themselves. This allows much better astrometric analysis because of the even distribution of individual stars on the CCD image. If the sidereal tracking were turned off, the stars would streak and the satellites would appear as star-like dots. Astrometry would not be as accurate with this method, however.

Figure 4: Tracking data from the CASTOR facility for the Telesat satellites Anik F1 and Anik F1-R. In this data, from left to right, the observation ID, time of observation (year, day of year, hour, minute, second, decimal second), and the determined coordinates (2000.0 R.A. and Dec.) are shown. This tracking data can be used to perform a more up-to-date determination of the satellite's orbit  in order to predict where the satellite will be in the future. Note how the declination of both satellites are several degrees below the celestial equator. Although these satellites orbit very nearly along the Earth's equatorial plane, CASTOR is located at a latitude of nearly 45 degrees. The parallax experienced changes the apparent location as seen by CASTOR to south of the celestial equator.

Figure 5: A CASTOR cropped image of the Russian Molniya 3-46 satellite taken on 06:21:35.670 to 06:22:15.670 U.T.C. October 2, 2005. Unlike the Anik satellites mentioned earlier, this satellite has a very uneven light curve. This suggests that the satellite is tumbling in space, and therefore inactive. The period of this tumbling can be determined using photometric analysis of the CCD image. The satellite is travelling left to right in this image (increasing R.A. and Dec.).


Figure 6: The results of the photometric analysis of the tumbling of satellite Molniya 3-46. Beneath the graph is the superimposed negative image of the tumbling satellite, scaled to match the time axis. Closer analysis of the data indicates that the satellite is tumbling with a period of about 8.7 seconds (or about 41.4 degrees per second in angular velocity). A vast database of satellite tumble periods for many satellites can be collected by amateur astronomers and can be analyzed for normal or sudden changes over time.


     I am not saying that all amateur astronomers should become satellite trackers. That would be an unfair statement on my part. Besides, not all amateur astronomers would like the subject, just like some amateur astronomers are not interested in observing planetary nebulae, for instance. Satellite tracking is an extremely new subject, especially if you consider that amateur astronomers have had access to it for only about 10 to 15 years.
     This article is not about institute bashing or discrediting bureaucrats as a whole. This article is simply stating that amateur astronomers can be a significant workforce in the satellite tracking community, but they would not be as enthusiastic about it if they had to fill out extensive paperwork to track them.
     Contrary to popular belief, the amateur astronomer does not require any special clearance from particular organizations (you know who you are) to start looking at and imaging artificial satellites. Many who aren't astronomers have seen at least a couple of low-Earth orbit satellites passing by while walking their dogs in the evening or early morning before sunrise. I always have fun when some ask me which satellite(s) they saw, given the time and location of the sighting with respect to the stellar background. Identifying an unknown satellite given limited clues is an interesting subject in itself!


     The amateur astronomer is extremely dedicated to the subject of amateur astronomy. The similarities between this subject and that of satellite tracking is enough such that the amateur astronomer has an advantage over those who have not experienced amateur astronomy in the field. Contrary to some beliefs, the amateur astronomer can begin tracking satellites with his/her own equipment right away. All he/she requires is a goto telescope, a CCD camera, a computer, and the enthusiasm and knowledge he/she has obtained from many hours of amateur astronomy. The worldwide amateur astronomy community can become a significant workforce dedicated to tracking our own satellite population. Amateur astronomers look at everything else in the heavens, why not artificial satellites too? Why would it be bad for amateur astronomers to track satellites for private satellite companies, and make a few bucks off it at the same time? These are some of the many questions that need to be answered within the realm of modern astronomy. When I first began tracking satellites, I fell in love with the subject. I would not be surprised if other amateur astronomers did as well. I myself love being a pioneer. I invite other amateur astronomers to do the same!


This page last modified: October 4, 2005