Spacewatch software was written for our project, and will only work with our detectors and computers; thus, we do not make it available.

But, there are many commercially-available software packages to choose from; these evolve rapidly, so this is a good question to pose in an active on-line discussion group of amateurs and professionals devoted to the detection of Minor Planets: the YAHOO! "Minor Planet Mailing List (MPML)" is one such group. Visit (and/or join) MPML at:


What you saw could have been one of three (or more) things, depending on its duration and apparent speed. Most likely, what you saw was a fireball, or a very bright meteor (shooting star). Usually, fireballs streak across the sky in a matter of seconds, but can leave a faint ionization trail visible for minutes. They can be as bright as the Moon sometimes. On the other hand, it could have been a satellite in orbit around the Earth. They are much slower moving and relatively constant in brightness. Many satellites are visible after sunset and before sunrise, as this is the time when they are reflecting sunlight but it is still dark on the surface of the Earth. Also, some satellites can flare up for a few seconds and become very bright when their solar panels reflect the sunlight. Finally, what you saw could have been a rocket launch or re-entry in your local area. These launches are sometimes visible for hundreds of miles, and generate a lot of curiosity!

If you wish to report a very bright meteor or fireball, do not report it to Spacewatch: once an object has entered the earth's atmosphere, it is no longer available for our telescopes to study. Instead, there are two organizations which would like to have your report, and each of them has an on-line means by which you can report your sighting easily. It is important to report your sighting quickly, because your report can sometimes help in the location and recovery of solid pieces of the meteoritic body which entered the atmosphere. The two organizations are the "American Meteor Society", and the "International Meteor Organization". To report your sightings, please use the links below:

American Meteor Society -- Fireball Report Form

International Meteor Organization -- Fireball Report Form

For general information from these two organizations about Meteors and Fireballs, please see:

American Meteor Society

International Meteor Organization

For many reasons, Spacewatch no longer hosts camera crews at the telescope.

You may preview selected videos online at our Spacewatch Videos website.

Thank you for your understanding!

The latest news about close passes of asteroids and comets by the earth can often be found at the astronomy magazine online sites, and the NASA Solar System Exploration site, which are updated very frequently. These are often the best, most reliable, and easiest to access sources of information on fast-breaking, important, news stories in Astronomy. We can recommend:

Sky & Telescope Magazine - A popular astronomy magazine online site; current events in the sky, and news items about Astronomy. 
Astronomy Magazine - Another popular astronomy magazine online site; current events in the sky, news items about Astronomy.

NASA/JPL Impact Risk Page - NASA/JPL Impact Risk Tabulation.

This is probably the most commonly asked question! While Spacewatch discovers and tracks asteroids, we do not calculate impact probabilities. That is the job of other institutions (MPCJPL NEO OfficeNEODyS). Currently, there are no known asteroids or comets that are on a collision course with the Earth in the predictable future. There are several potentially hazardous asteroids that have orbits which could make them dangerous sometime in the future. However, currently none of these objects poses a danger much above the background chance that the Earth is hit by something not yet discovered. You can check the close approach distances of all known Potentially Hazardous Asteroids (PHAs) on the PHA Close Approaches To The Earth page.

Throughout Earth's history, we have been bombarded by comets and asteroids from space. Impacts have happened before, and they will happen again. It is just a matter of when. This is one of the main goals of Spacewatch, to look for the potentially dangerous objects well before they pose a threat.

Spacewatch pioneered the use of "Drift-Scanning" with CCD's as a way to maximize the amount of data they could collect with their telescope. Stars and asteroids, just like the Sun and Moon, are affected by the Earth's rotation. They rise in the East, move overhead, and set in the West over the course of a day. Most telescopes will move to whatever target they wish to observe, use the telescope's motors to follow the target, take a picture with a CCD and then read the picture out so it can be examined. The problem with this method is that for most CCD's the read time can be longer than the exposure time and so you only use half (or even less) of the night actually measuring the night sky.

Spacewatch, under Tom Gehrels, pioneered an alternate way to use a CCD camera that avoids this problem. Instead of going to the target of interest you lead it a little bit on the sky then you shut the telescope drive off. The stars start to move ("drift") across the CCD. If you exposed the CCD and then read it off they would appear trailed along the direction of the sky's motion since you didn't use motors to track them. However, Tom lined up the CCD with the sky and then started the CCD reading at exactly the rate at which the sky was moving. The stars therefore appear round and the resulting picture is really long without any read time wasted. You didn't get something for nothing, however, since the first bit of the data (the "ramp frame") is hard to use and the exposure time is fixed for the instrument. However, drift scanning was a very unique solution for Spacewatch's survey needs. It has since been copied by several other large surveys and is gaining popularity with amateur astronomers around the world.

The only organization with internationally-recognized authority to name asteroids is the Committee on Small Bodies Nomenclature (CSBN) of the International Astronomical Union (IAU). We Spacewatchers, as members of the IAU, subscribe to and recognize that authority. In the case of asteroids with orbits good enough to receive permanent numbers from the IAU's Minor Planet Center (MPC), names may be suggested by the discoverers. Suggested names are reviewed by the CSBN and the approved names are announced periodically by the IAU. A description of how objects are named can be found in:

Public Naming of Planets and Planetary Satellites (PDF) 

While it is true that Spacewatch DETECTS hundreds of asteroids per observing night, detections on single nights are inadequate to establish accurate orbital elements. That accomplishment requires many more observations spanning years. So only asteroids that are repeatedly re-observed (deliberately or serendipitously) finally receive permanent numbers. Amateur astronomers regularly observe asteroids, and their work is extremely valuable in increasing the accuracy with which asteroid orbits are known.

As of 2000 Sept. 12, Spacewatch had been credited with 231 asteroids that had advanced to the stage of receiving permanent numbers from the MPC. Spacewatch has suggested and received approval on the names of several asteroids. These names are usually selected from among our scientific colleagues, especially those who have worked in the discipline of asteroid science. Nevertheless, we, as discoverers, do not have direct naming rights, and must be careful not to PROMISE in advance that the IAU will name an asteroid after any specific person, because every nomination is voted on case-by-case by the members of the CSBN.

This constraint is not an explicit prohibition against naming asteroids after generous philanthropists, but before any observers start offering asteroid names for money, the search community should agree upon some ground rules so that different groups will not start competing with each other for the "price" of an asteroid name. That kind of auctioneering of the process of naming celestial objects might discourage the IAU from cooperating.

One could also get into complications like what type of asteroid is being "purchased". Asteroids have to have very well-determined orbits before the IAU will name them. It is a great deal more work to establish orbits of some classes of asteroids than others. How are we to take into account in the "price" the number of observations, the span of years needed to establish a numberable orbit, the observers other than the original discoverer who made vital recoveries of the object before its orbit was accurately known, and the computational creativity of the MPC in linking observations of the same object made many years apart?

Offering names that are NOT endorsed by the IAU would not be fair to the "customers". For background on this issue by analogy with star names, see

Buying Stars and Star Names 

The implications of naming asteroids after contributors on the tax-deductible status of their contributions has not been addressed here, because we are not lawyers.

This is a complicated issue, and that is one reason Spacewatch has not been selling asteroid names.

The images on this website have been optimized for viewing over the internet, in terms of image size and file size. Most color photographs are stored in JPEG format, allowing for true color and fast downloads. Many of the CCD images of asteroids and comets are stored in GIF format, to better represent the quality of the original. Our images of asteroids appear 'grainy' because the image displayed is only a small, magnified cropping from the original CCD image. They were magnified to make the asteroid's movement easier to see, but no pixel information was lost. So the images of asteroids on the web page are as high resolution as they can get.

All Spacewatch material, unless otherwise credited, is copyrighted by the Arizona Board of Regents, with which all rights are reserved. No part of Spacewatch material may be copied, reproduced or transmitted in any form without written permission in advance from:

Dr. Robert S. McMillan 
Principal Investigator, Spacewatch Project 
Lunar and Planetary Laboratory 
Kuiper Space Sciences Building 
1629 East University Blvd. 
The University of Arizona 
Tucson, AZ 85721 


We are glad to hear of your interest in our work. Please try to learn as much as you can from our publications, our web site, and the other sites to which our site links before requesting personal help. When you finally do have questions that aren't answered by our papers, it helps us if you tell us how much you already know about the subject and what you have already done to find the answers you seek. That is the most educational way to do research for school, and it helps us to write answers at your educational level.

All positions for staff, faculty, and graduate assistantships in the Spacewatch Project would be advertised on this web page by means of a link to the official advertisement on the University of Arizona Human Resources web site. If no "Job Available" link is present on the main Spacewatch page, that means there are no openings at the present time. If there is a "Job Available" link, please follow the procedure for application that is described in the ad.

Thank you for your interest! Spacewatch does not regularly seek nor do we regularly employ volunteer workers. An important way of helping our work, however, and of advancing the NEO field generally, would be for citizens such as yourself to express to your Senators and Representatives your appreciation of the importance of NEO work. Spacewatch is a major planetary resource in the effort to discover and monitor NEOs which could pose a hazard to the Earth by colliding, or which can become mineral resources in future by being mined while orbiting the sun. When you write, phone, email, or FAX your Senators and Representatives (or all of the above!) to encourage them to fund NEO research, you will be helping Spacewatch and the entire NEO field, as well as Solar System Science in general. Very few of our elected representatives are scientists, and they need to know that they have their constituents's support in advocating for scientific research and for NEO research in particular. Thank you for this very important and valuable support.

There used to be.  In 2003, Spacewatch started the "FMO Project" courtesy of funding from the Paul G. Allen Charitable Foundation. This effort ended successfully and fruitfully in Spring of 2006. To read about the project and to see the results, you may access our FMO Project webpage through FMO Project.

Each planet in the solar system exerts some force on the Earth, however small that force may be. Most of it comes from the sun and the moon. For example, the moon is the primary reason we have tides. As you may know, twice per month there is a higher than usual tide. This occurs when the sun and the moon are lined up and acting to "tug" at the Earth in the same direction -- causing more pronounced tides. No other planets contribute to the Earth's tides because they are very far away, and gravitational force varies inversely with the square of the distance. Even if all other planets were to line up, the combined magnitude of their gravity would be insignificant compared to that of the sun and moon. It wouldn't even be detectable! So, in short, if there is a planetary conjunction in the sky, go out and watch it in comfort and with appreciation. For more "coverage", please see the popular astronomy magazines or their websites.

There are several flavors of space object tracking software available on the internet - some free and others that cost some money. If you are looking for software that will show an object's position (RA and Dec) in the sky, there are numerous planetarium programs that do that. There are also programs that give a "space view" of the solar system from anywhere in the solar system. Here are a few sites worth checking out that may be of help:

The Minor Planet Center 
Near Earth Objects Dynamics Site 
JPL Horizons

Also, search the web for "astronomy software" for more information on programs that are available.

  • The End of the Dinosaurs, by Charles Frankel, Cambridge Univ. Press, 1999.
  • Rain of Iron and Ice, by John Lewis, Addison-Wesley, 1996.
  • Mining the Sky, by John Lewis, Addison-Wesley, 1996.
  • Comet and Asteroid Impacts on a Populated Earth, by John Lewis, Academic Press, 2000.
  • Comets, Creators and Destroyers,by David Levy, Touchstone (a division of Simon & Schuster), 1998.
  • Rogue Asteroids and Doomsday Comets, by Duncan Steele, Wiley 1995

These are more technical but very good:

  • Asteroids II, Edited by Tom Gehrels, Univ. of Arizona Press, 1989.
  • Asteroids III, Edited by W. Bottke et al., Univ. of Arizona Press, 2002.
  • Hazards Due to Comets and Asteroids,Edited by Tom Gehrels, Univ. of Arizona Press, 1994.

Thank you for your interest. Unfortunately, Spacewatch does not offer training for other observing programs. There are too few of us to have time to teach anyone else, and our equipment, software, and methods are too different from what everyone else is using for such an effort to be worthwhile. We suggest that you contact the Minor Planet Mailing List and ask whether you could visit someone who uses software and equipment similar to what you would be likely to procure for yourself.

Key to the designations is given in the table below:

Prefix      Survey Name     COD        Era
------   -----------------  ---  -----------------------

FS-nnn = First Spacewatch   691  circa 1984-1988)
SS-nnn = Second Spacewatch  691  circa 1989-2002 Apr 23)
ts-nnn = Third Spacewatch   291  circa 2001-2011 Oct 1)
SW4xxx =  4th Spacewatch    691  2002 Apr 24 -present)
SW5xxx =  5th Spacewatch    291  2011 Oct 16 - present)
SW6xxx =  6th Spacewatch   ^695  2010 - present) using KPNO Mayall 4-meter telescope.
SWBxxx =  Bok Spacewatch   ^695  2016 Apr 18 - present using Steward Bok 2.3-m telescope.

where "nnn" = an integer from 001 to 999 and "xxx" = a heirarchical
string of characters running sequentially through digits 0-9,
letters a-z (lower-case), followed by A-Z (upper-case).

From 1984 April through 2002 April 23, COD 691 was the Steward
Observatory  0.9-meter f/5 Newtonian telescope with various CCDs
of increasing size with time (also see: 0.9-meter telescope
equipment epoch table).

COD 691 is presently a 0.9-meter f/3 telescope with corrected
prime focus and four CCDs in a mosaic covering an area of 2.9
square degrees (also see: 0.9-meter telescope equipment epoch

COD 291 is the Spacewatch 1.8-meter telescope with a 2048x2048
CCD at folded, corrected f/2.7 prime focus (also see: 1.8-meter
telescope equipment epoch table).

Yes! By all means, if you want to link to us, please do!

Title: The Spacewatch Project 
URL: http://spacewatch.lpl.arizona.edu

If your site has appropriate scientific value or content, email the Spacewatch Webmaster about it. We will inspect it and let you know about its suitability or unsuitability for linking by us. We cannot link to sites arbitrarily, without investigating whether the site has bearing on our field. Thanks for your understanding and consideration in this matter.