SeeSat-L Home Page


SeeSat-L is the mailing list for visual satellite observers. It was created in December 1994 by Walter Nissen and Bart De Pontieu. Since July 2002, it has been maintained by Ted Molczan. Mike McCants became co-administrator in 2014.

Thanks to the diverse interests of its participants, SeeSat-L has become an almost indispensable tool for the satellite observer, providing him/her with :

Rules and Guidelines

Purpose and Acceptable Use

SeeSat-L is intended to facilitate rapid, reliable communications among visual satellite observers. Visual observations and CLOSELY related subjects are its sole focus; all else are off-topic.

SeeSat-L is intended to be the big tent under which our small but diverse hobby can thrive. We are accepting of all who contribute, regardless of their experience or area of special interest. For example, beginners are welcome to describe their sightings of the ISS, and those who make positional or flash period observations are welcome to post their mostly numerical data.

Personal attacks against anyone are not tolerated on SeeSat-L; fortunately, such incidents have been rare.

If someone has posted something that you believe to be off-topic, or that you find abusive or offensive, please do not post a response to SeeSat-L, but please do e-mail your concerns to the administrator.

If you have suggestions regarding the operation and use of SeeSat-L, please feel free to send an e-mail to the administrator.

Communicate Observations Clearly

Please state the date and time of your observations, preferably as UTC (co-ordinated universal time). If you use local time, please state whether or not it is standard or daylight-saving time, and state the number of hours ahead or behind UTC.

If your observation includes positional information, whether descriptive or numeric, please include the latitude and longitude of your observing site, or at least the geographical name of the place. This data is especially important if you are requesting assistance to identify an unknown satellite.

If you plan to report positional observations regularly, please use one of our standard positional observation reporting formats.

If you plan to report flash observations regularly, please use the standard PPAS observation reporting format.

If you know the identity of the object you observed, then you should include its catalog number and/or international designation. You may also include its name.

Reporting High Resolution Ground-based Imagery of Earth Satellites

SeeSat-L welcomes reports of high resolution ground-based imagery of Earth satellites. Effective 2011 May 16, the following supporting information is required:

1. ID of object: COSPAR, USSTRATCOM catalogue number, common name

2. Description and dimensions of object (metres), if known.

3. Observing site location: latitude, longitude, altitude, to nearest 100 m

4. Date/time of obs: UTC. For single frames, report time to nearest second. For video, report start time and duration to nearest second.

5. Range to object: km

6. Telescope: make/model/aperture

7. Camera: make/model

8. Tracking method: hand-guided, or mechanical (make/model)

9. Data acquired: total duration, frame rate, exposure per frame, resolution & bit depth of raw data

10. Processing: describe the process of frame-selection and/or image-processing used to obtain reported results.

11. Raw image frames: Results consisting of one or more frames selected from a longer series of frames, whether image-processed or not, must be supported by at least 60 seconds of the complete set of raw frames centred on the time of the results, i.e. 30 s before and after. By raw frames is meant the data exactly as taken from the camera that formed the input into the process of frame-selection and/or image-processing that produced the result. If the result is displayed on a web site, then a link to the raw data should be located in close proximity. An alternative would be to place a statement that the data is available upon request in close proximity to the results.

Do Not Post Elements Originating from Space Track

When posting to SeeSat-L, you must comply with's user agreement, by not posting elements or other data, e.g. RCS values, that originated from that site. This SeeSat-L rule also includes elements of unclassified objects obtained from NASA/OIG or third parties - even those who have Space Track's permission to distribute elements, since it is almost impossible to later prove how the data was sourced. This applies also to historical elements, since most of those now are also available from

Where past practice was to include an elset of an unclassified object to substantiate an argument, now it is best to state only its name, international designator, catalogue number and perhaps the epoch or serial number of the elset in question, and leave it to interested readers to obtain the actual elset, or include a link to a source.

Plain Text Only, With No Attachments

SeeSat-L accepts only plain text messages (not html and not rtf), without attached files.

Please avoid:

Subscription Info

You can subscribe to SeeSat-L, and manage all aspects of your subscription, via the web:

Alternatively, you can subscribe by sending commands via e-mail:

Your (un )subscription request will be automatically handled by the software, so please make sure you follow the instructions above EXACTLY.

Read the SeeSat-L Archives

Read past SeeSat-L messages at our Hypermail-Archive.

Search the SeeSat-L Archives

Google search the domain, i.e., mostly the SeeSat-L archives. Note that Google sometimes takes a few months to update their archives of our site.

Tip: To avoid cluttering your search results with monthly index pages, include the following search term: -"other mail archives"

Search Link: to the VSO Home Page