International Astronomical Center

In This Page:-

• Introduction
• SRW Objectives
• Who Are We?
• Join Our Mailing List
• FAQ
• Submit Your Sighting
• SRW Identified Reentries
• Links to Related Websites
• Reentry Predictions
• Reentry Videos
• Reentry Events in the Media

Space debris continues to fall from the sky on a regular basis. Much of this goes unreported either because little attention is given to it by casual observers or reentries are seen from places where few people live or because eyewitnesses simply do not know what they are seeing. Meteors, which are natural debris, fall daily and are seen as fast moving streaks though some times as brilliant fireballs.

Artificial satellites are more rare but can appear as a single object that transforms into a procession of slow moving lights. We encourage all readers to provide an accurate report online as soon after seeing such an event using the form found below in this page.

Note that observations of UFOs or meteors are not being requested. A spacecraft reentry has a unique signature as described above and it will be quite obvious if you see such a group of objects traveling together in formation with some disappearing while others continue in parallel flight paths.

A UFO (unidentified flying object) can be interpreted in a number of ways. Stars, planets, the Moon and Sun are all essentially stationary objects. The only reason they seem to 'move', is that the Earth rotates slowly and collectively they change their position in the sky gradually throughout the night (or day). Flying objects may consist of individual birds or flocks of birds, bats, airplanes, military flares, possibly balloons, lanterns, even glowing insects like fireflies. Other moving objects are generally star-like and these are normally spacecraft and other satellites in Earth orbit. Airplanes flying from one place to another may appear star-like but are often accompanied by adjacent red or blue lights. Most untrained observers, news media, so-called 'official sources', law enforcement, military and government personnel are not able to tell what they are seeing. Thus, a UFO to one person may not be a UFO to another. Many reports of UFO's can be linked to streaks in the sky that are most often spotted after sunset or before sunrise. These are usually linked to rocket launches and can be spotted soon after launch or minutes or hours after a launch in relation to rocket stage separation. Still others might be classified as 'unexplained'. This site does not accept reports of this nature and the reader must think through carefully prior to submission.

Collection of evidence is crucial to any report. A video taken with a camera mounted on a stable tripod and clearly focused is a valuable tool to support any investigation along with accurate time and location details.

The objective of SRW is mainly an educational one. We aim to spread awareness on this subject to the general public and the astronomical community through the following methods:

1. Send alerts to our members before an expected reentry.
2. Ask the interested members to observe an expected reentry and report back their sighting.
3. Discuss this subject in the mailing list of SRW to increase the knowledge of the members.
4. Send news reports to the media, if required, about major reentries that were witnessed over large areas.

SRW is a collaboration program between international experts in the field of artificial satellites and the International Astronomical Center (IAC). Any interested person is welcome to join the program. SRW is moderated by five supervisors, who are (Sorted Alphabetically):-

1. Joseph Remis: Expert in satellite reentry predictions.
2. Marco Langbroek: Expert in artificial satellite observations.
3. Mohammad Odeh: IAC director.
4. Paul Maley: Space debris and satellite observer.
5. T.S. Kelso: Professional expert in satellite tracking and observation.
6. Ted Molczan: Expert in artificial satellite observations.

We have created a dedicated mailing list for SRW, where interested persons can join it and start discussions and share their knowledge. We will send reentry alerts to this mailing list as well. Kindly click on the link below to join the mailing list (Group).

Below are some Frequently Asked Questions (FAQ) regarding satellite reentries.

1. How many satellites orbit Earth? and how many of which are operational?
   A: This number is constantly changing as new satellites are launched and others reenter the atmosphere. As of June 2021, the United States Space Surveillance Network (SSN) tracks more than 23,000 objects orbiting Earth. About 20 percent of those being tracked are active payloads, the remaining are rocket bodies, debris and inactive satellites. Out of the 23,000 tracked satellites, about 17,000 are available to the public. According to “SATCAT Boxscore”, as of 28 May 2021, there are 7532 payloads (4538 are active), and 15708 debris orbiting Earth that are currently being tracked. There are thousands of much smaller pieces of debris that cannot be tracked due to their size.

2. Why do satellites decay and will all of them reenter Earth?
   A: Satellites that are launched into Earth orbit decay due to the effects of gravity, intentional deorbit by the spacecraft owner, solar radiation pressure, lunar and solar perturbations and interaction with the atmosphere. Generally speaking, the higher the overall orbit, the longer the satellite will remain in orbit. Satellites in geostationary orbit will remain there and not decay.

3. What happens to a satellite during reentry?
   A: As the object begins to descend from orbit it encounters layers of molecules that compose the atmosphere. As the density increases, the object begins to heat up at an altitude of about 400,000 ft (75 miles or 122km) during its descent. The weakest pieces of structure, and also lighter parts, begin to break off. Some will disintegrate quickly with others taking more time. Explosions may or may not occur. Some pieces may survive reentry and others may skip back up into orbit reentering some hours or minutes later.

4. How does the reentry look like in the sky?
   A: A reentry has the following appearance. A single star like object moving slowly through the sky will accelerate. Multiple objects will begin to appear until a long procession of objects can be observed. Some appear and disappear quickly while others linger. The whole process, depending upon when you first spotted it, could take from maybe 20 seconds to a minute, but these times could be also longer or shorter in duration. The objects may appear white, yellow, orange, red or blue depending upon how your eye perceives them.

   A smoke train may be left in the wake of a reentering satellite path lasting a fraction of a second to many seconds in length, but this phenomenon is more closely connected to bright fireballs. Sounds such as sonic boom(s) may accompany the passage of either a very bright fireball or a very spectacular satellite reentry. The term 'satellite reentry' applies to satellites, rockets or other pieces of man-made orbiting objects.

5. What are the most common types of space objects that survive reentry?
   A: Titanium pressure spheres have a very high melting point and are the most common objects found to survive reentry.

6. What are the definitions of some terms used in a reenty event?
   A:

   - Reentry Trajectory: is the end of the final orbit where the decaying object is burning while going down. The length and the time of course of this trajectory depend on the object. Example: for a rocket body this trajectory is some 1000-2000 Km long and has a 2-4 minute duration while altitude decreases from 130 to 80 kms.

   - Reentry Viewing Location: it is the regional area on Earth from which the burning decaying object is visible.

   - Debris Footprint: the projected area at the end of the reentry trajectory where surviving debris could impact the planet either on land or water.

   - Impact Location is a point at the end of Footprint where an impact of a decaying object occurs.

7. At what altitude does a satellite begin to reenter the atmosphere?
   A: A satellite starts to reenter around 400,000 ft (75 miles or 122km). Low melting point materials melt first, exposing remaining material to the extreme heat and forces of reentry. As pieces melt or break away, the heating and deceleration loads increase, further breaking the object apart and creating multiple pieces of debris some of which may or may not survive reentry.

8. What is the altitude regime where reentry can be seen?
   A: The reentry may be seen from an altitude of approximately 122km to a much lower altitude, perhaps as low as 40km. These altitudes are not precise and are rough indicators based on atmospheric density.

9. Where might debris from a reentry land?
   A: The area where debris might land is called the debris footprint. The heel of this footprint is approximately located under the breakup point, and its toe might extend up to 2000km/1240 miles downrange (that is, in the direction of the flight path); the width of the footprint varies from 20km/12 miles to 40km/25 miles.

10. Does the expected reentry location mentioned in the predictions represent the same location where the debris might hit Earth?
    A: No; “reentry location” is not as same as “impact location”. A reentry may be predicted by one or more official sources, therefore, reentry location/time predictions may not be identical since each source may use a different model. One source may define the reentry location/time as the location/time at which the altitude of the satellite is 80km/50 miles while another might adopt the altitude as 10km /6 miles. SRW sends out predictions for 3 possible orbits showing an area that appears to indicate a 'reentry location'. However, as each new prediction update is issued, that potential location area will change. But it is not exact by any means. So, observers are recommended to consider any zone underneath all 3 orbits a location where the reentry might begin.

11. Are reentries more likely to be seen in Europe or North America than in Africa or the Middle East?
    A: Not really. Most satellite orbits lie between latitude 28 degrees and 82 degrees. Most of Earth's inhabitants live in that range of latitude either north or south of the equator, however, some reentries from equatorially launched objects might also be seen between 0 and 4 degrees latitude north/south.

12. How often does a satellite reentry occur?
    A: For tiny debris: Perhaps 0 to 5 objects per day. For payloads, rockets and big debris (Radar Cross Section > 0.5 m²): approximately one per week. In comparison, thousands of small pieces of meteoric debris reenter each day and some of them appear after sunset and before sunrise as 'meteors' or 'fireballs'. A few may easily be mistaken for reentering satellites.

13. What sizes of space objects create visible reentry tracks in the sky?
    A: Objects from inches/centimeters in diameter or larger are potentially capable of being seen by ground observers. Objects smaller than this may be seen as well as typical meteor streaks.

14. Can reentries be seen in daylight?
    A: Generally, no. Brilliant fireballs (meteors or small asteroids) may on rare occasion be seen in daylight.

15. Is it true that a reentry can only be seen far from city lights?
    A: No, reentries have been witnessed from brightly lit stadiums as well as from inside urban areas at night.

16. How accurate are satellite reentry predictions?
    A: Reentry predictions are inaccurate for many reasons: the main one is the variation in the density of the upper atmosphere depending on solar activity. The orbital elements used for predictions are also inaccurate due to errors in the observations (mainly radar) used to compute them. The uncertainty is approximately 20% of the remaining lifetime of the object. When the final reentry orbit update has been provided it is possible that for a given location the variation in the actual pass time might be + or - 2 minutes. Usually three orbits are shown, one before and one after the predicted reentry orbit. Observers under any of those last orbits should be alert for a possible reentry.

    Normally SRW sends out alerts for unique reentry possibilities. For any given reentry candidate, more than one update is usually sent out. Do not rely on the area of predicted reentry until within 12 hours of the projected update as all predictions will have an inherent error in them. Predicting the exact area and location of a reentry is an inexact science. Every effort is made to use the best software predictions and most recent orbital elements in order to maximize the chance of witnessing such a reentry. Even though satellites have been reentering the atmosphere for more than half a century reentry prediction is still an evolving art.

17. If I go out and look for a reentry during the suggested window of time and do not see anything, is this information of any value?
    A: Yes, if the sky was clear and you were looking consistently during the suggested time period and did not spot the reentry, this negative observation tells us that the reentry did not occur from your geographic location and on that predicted orbit. It may be used to confirm other negative or even positive observations and place limits on the actual reentry zone.

18. I know a reentry was witnessed years ago from my country. Would SRW be interested in such old information?
    A: Yes. There may be accounts of reentries or even space debris found and left in a museum which was not widely reported. Please send that to us.

19. Is a reentry considered dangerous?
    A: After more than 50 years of space launches, very little damage or injury have been reported as a result of reentering space objects. The odds of being killed or injured by a piece of space debris are quite small but not completely zero. Damage or injury could result from the velocity at landing and mass of the landed object. Danger could exist if the object contains radioactive material -quite rare- or hypergolic propellant or other chemicals that could be toxic or explosive. However, rocket stages that do not reach orbit (by intent or accident) have been known to fall back to the ground causing damage to property and starting fires. The same can be said for launches that explode after launch.

20. Why are observations of reentries important?
    A: To better understand where and when a particular space object came down. This may help quantify reentry prediction accuracy or enable identification or discovery of space debris. They are important to those attempting to study the cross range and down range dispersions of fragments and composition of objects that survive reentry.

21. If you have been alerted to a reentry, should you contact the media?
    A: No. The reliability of most reentry predictions is quite poor. Alerting the media is likely to be a non-productive effort unless you are very lucky.

22. Should you rely on testimony from police or military officials over that provided by civilian accounts?
    A: No. There may be politically motivated and sanitized reports provided from such 'official sources'. It is better to have independent eyewitness reports to help corroborate 'official' accounts.

23. Can you rely on eyewitness accounts from people who have no experience observing at night?
    A: No. We take reports from amateur or professional astronomers more seriously than untrained eyewitnesses. Most untrained observers are unable to provide detailed descriptions of objects in the night sky, especially if their appearance is short-lived. Vital information that is critical to identification include exact time of the observation, brightness in comparison to known objects in the sky, direction of motion, direction of start/end of trajectory. Untrained observers are unlikely even in the daytime to be able to identify even cardinal points (north, south, east, west).

24. If you find genuine space debris, does it belong to the finder?
    A: This can be an interesting topic. Some genuine pieces of space debris may contain markings that might enable identification in Cyrillic, English or another language. In other cases no markings such as numbers and letters will appear. It can be embarrassing for a launching nation or entity to admit that a piece of debris has survived reentry especially if it caused or could have caused damage or injury. There is implied legal liability. Thus it may be that no one will claim it is theirs. If it falls on private property, then it is likely the owner of that property has right of initial ownership. You should consult international laws governing ownership of recovered space debris.

25. Does recovered space debris have monetary value?
    A: It may on sites like eBay. But the real value may lie in scientific analysis by entities such as NASA.

26. If I find a piece of space debris can I legally sell it on an internet site or through a private sale?
    A: Technically it may be illegal to sell such a piece of debris on the open market, especially if it has markings clearly identifying the country of origin.

27. What should I do when I see a suspected reentry event?
    A: Attempt to determine whether or not your sighting was a meteor, aircraft or something else given our advice. If you can safely eliminate these possibilities and the appearance was similar to the reentry description, then please file a report.

28. How do I know if what I see is a meteor, airplane, satellite reentry or UFO?
    A: A meteor may move quickly across a small or large portion of the sky in a matter of a fraction of a second to perhaps as long as 10 seconds---but longer in extreme cases. It may appear in any part of the sky and move in any direction. A bright fireball may have similar appearance and could break into 2 or more pieces. Meteors may appear individually or as part of a meteor shower.

    A satellite in orbit may appear to travel in the direction of the Earth's rotation -- west to east, southwest to northeast, northwest to southeast, north to south or south to north. If you see it moving from east to west, southeast to northwest or northeast to southwest you can be almost certain that it is NOT a reentry. This is because most satellites are launched into orbits using the Earth's rotation to expend less energy than if launched against the Earth's rotation --retrograde. Usually a satellite is seen as a singular object when in orbit. A satellite reentry's appearance is described by another FAQ.

    An airplane may appear star-like and appear anywhere in the sky. Sometimes you can hear sound from engines as the plane passes over. The star like object may be flanked by a red light on one side and blue light on the other, with all three lights moving close together and parallel.

    A UFO is something other than these descriptions. It may involve one or more stationary or moving lights of single or variable color. Movement might be sporadic or quick. The position may change or not. It may fade and then reappear. It may also appear like a small or large cloud in an otherwise clear sky. These are just some of the many forms of UFOs. Direction and speed are not predicted nor is duration. These may be spotted closer to military bases or rocket launch sites or proving grounds but others can appear any place or time, day or night. We are not in a position to investigate so please do not report them.

29. If I saw a glowing object as being red, but someone standing next to me saw it as green, what does that mean?
    A: Each person's eyes have a somewhat different way perceiving a bright object against a black background. Some people have poor color perception or night vision, may suffer from astigmatism or not be using glasses or contacts as they should at the time of observation. It is often difficult to have universal agreement amongst eyewitnesses. The best way to understand this is in real life. The same experience can occur in a legal courtroom where eyewitnesses are asked to describe what they saw and no two individuals describe the same scene identically.

30. How long should I wait before filing a report?
    A: File the report as soon as possible while the details are fresh in your mind. We recommend that you report your observation within an hour and no longer than 12 to 24 hours after your sighting. Memories begin to fade quickly.

31. What will happen to my report after I submit it?
    A: Your report will be read by SRW representatives who will attempt to assess its validity. Whether the report is related to a reentry or not, SRW representatives will provide an email feedback as soon as a decision has been reached. This might be quickly with additional information requests especially if it can be immediately tied to a reentry. If there have been many reports it could be several days or more. If your report cannot be connected with an event, we may recommend you contact another body such as the International Meteor Organization.

32. What is a good way for me to better understand directions at night?
    A: Carry a compass or GPS unit or smart phone that has a compass feature. The best way is to learn the constellations so you can more easily identify North, South, East and West.

33. What equipment do I need in order to make useful observations or reports of a reentry?
    A: You do not need a telescope. A pair of binoculars may be of some use, however. A voice recorder and time signal receiver would be helpful to accurately link details of the reentry to the correct time. If you have wristwatch, unless it is accurately calibrated to a known time source, the time will only be approximate. It also could be in considerable error. It is best to record what you see to the nearest minute (AND second if possible). Your eyes, if they are 20-20 with glasses/contacts or normal vision make the best 'sensors'. It helps to have other, younger observers with you who have confirmed good vision. Please determine ahead of time if you or others suffer from color blindness, near-sightedness or other vision ailment so this may be reported. A tripod-mounted 35mm camera with shutter release set to ISO 400 or higher and 15 second exposure (or longer). You can also use a video camera or even a smart phone with video capability is also good for documenting what you have seen provided you are able to focus, point and activate your device in time. Test to be sure your camera focus is set to infinity prior to going outside to look.

34. Can a photograph be of use in place of video for a reentry?
    A: Yes, provided certain conditions are met. The photographer must have some prior knowledge that a reentry may happen near his vantage point. Then he or she can arrange to set up a 35mm digital camera on a stable tripod with a shutter release. The ISO should be set to 1600 or higher and the camera placed far from lights. The exposure should be pre-set to 'bulb'. The photographer, knowing what direction to look based on the reentry prediction should use a wide angle lens -e.g. 14mm- on the camera. When the reentering satellite is seen and understood to be real, the photographer leads the reentry so the field of view is placed just ahead of the flight path. Just before the reentry passes through the field of view, the shutter release should be activated. The reentry will then cross and exit the field of view. Then the shutter is closed. If there is time a second photo may be taken in the same manner. It would help if the internal camera clock has been accurately set to the local date, hour and minute. This information can then be retrieved after the photo is downloaded. It is important to document the direction in which the camera was pointed, but if the exposure is long enough and the sky is devoid of cloud, stars will embed themselves in the image and the flight path may be recognized against the star background. Video is more useful since it grabs a frame each .033 seconds but if the sensitivity of the video is not good, only the brighter pieces may be captured.
35. How do I know that either my 35mm camera will work or my video camera will be effective in documenting a reentry?
    A: Practice pointing both at bright stars. For the video camera see if you can manually open up the lens as far as possible to determine the level of minimal star brightness that can be clearly recorded. For the 35mm camera, take 15 or 30 second test exposures of the sky and see the level of brightness of stars that can or cannot be recorded. You must never take such a camera to a reentry without first having tested it, charged batteries fully, or focused it on stars prior to the reentry.

36. What are the most important things to think about in photography or video of a reentry?
    A: Proper focus is the most important thing to verify before the reentry session. Testing the camera by pretending/simulating a reentry many days before will help ensure good documentation. Avoid hand holding a video camera. Mount on a secure tripod and on a stable surface that will not give way during the reentry just as you must do with a 35mm camera. Point and shoot cameras are not to be used.

37. Should I be using the zoom feature on my video camera?
    A: Probably not. But test it on a moving airplane at night and see if the image remains in focus. Zooming in and out consumes battery power and may result in a field of view that is too small to contain reference objects such as bright stars or buildings which are necessary to help in the post reentry analysis.

38. Why are you not able to process UFO reports?
    A: Such reports take too much time and resources to investigate. SRW personnel are volunteers who have limited time and resources.

39. If I have seen a meteor, fireball or UFO, should I send you this sighting?
    A: No, we are not interested in such events. Meteor/Fireball observations can be sent to http://www.imo.net/ or http://www.amsmeteors.org/ , while suspected UFO sighting can be sent to http://www.nuforc.org/ or http://www.mufon.com/ .

Below is a table for some satellite reentry events which were identified or followed up by SRW program.

• Paul Maley’s SPACE DEBRIS PAGE

• SatTrackCam Leiden (b)log

• VSO Satellite Re-entry Page

• Center for Orbital and Reentry Debris Studies

• NASA Orbital Debris Program Office

• Visually Observed Natural Re-entries of Earth Satellites, by Ted Molczan

• Liability/Responsibility Page of The European Centre for Space Law (ECSL).

There are several resources for satellite reentry predictions. Some differences might be noticed from site to another. We recommend adopting the predictions given by Space-Track (USSTRATCOM) as a primary resource. While the “Visual SAT-Flare Tracker” website can be used for watching the location of the satellite over Earth.

• Space-Track (USSTRATCOM)
  

• Visual SAT-Flare Tracker Online
  

• SATVIEW Tracking Satellites
  

• Cosmos 1220 reentry over Hail in Saudi on 16 February 2014 at 01:40 UT.
  

• Chinasat 9 Rocket reentry over Saudi on 16 January 2014 at 20:07 UT.
  

• MIR reentry near Nadi, Fiji on 23 March 2001.
  

• Jules Verne ATV reentry over the Pacific Ocean on 29 September 2008.
  

• Japanese Satellite (Hayabusa) reentry over Australia in June 2010.
  

• SKYLAB Space Station Wreckage.
  

• Cosmos 1220 Reentry over Saudi on 16 February 2014 at 01:40 UT in the Saudi Newspaper Sabq. (Arabic)
  

• Cosmos 1220 Reentry over Saudi on 16 February 2014 at 01:40 UT in The Independent Newspaper.
  

• Chinasat 9 Rocket Reentry over Saudi on 16 January 2014 at 20:07 UT in the Saudi Newspaper Sabq. (Arabic)