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International Space Station Sightings category

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Here's my attempt to make the category description shorter, and a little easier to understand. Requirements have not changed. The biggest differences are 1) the absence of the "detailed step-by-step instructions", and 2) the addition of Visiting Requirements (previously they were on a geocache page).

The detailed instructions can be very helpful, but they make for a much longer category description. Any ideas of where I could put them for those who want to read more? Do you think they should be included in the category description? This section would add a lot to the length. I'll post them separately.


This is a game that requires two or more players to "catch" the International Space Station as it visibly passes through the night sky across hundreds or thousands of miles in one of its orbits around the globe.



Expanded Description:

This relatively simple challenge is to observe the International Space Station (ISS) one minute before or after at least one other player sees it from their location. Participants need to be at least one minute of ISS travel time (293 miles or 472 km) apart, and the ISS must reach at least 45° altitude for all players located below 55° N/S latitude* All players will have to observe the ISS during the same visible pass.

A visible pass is the time period that the ISS is sun-lit during its flight through the night sky. A visible pass begins just after Sunset when the ISS becomes visible in the night sky and ends when the ISS enters the Earths shadow and is no longer visible. A visible pass can also occur when the ISS comes out of the Earth’s shadow, is visible in the night sky, and ends when morning daylight makes it no longer visible.  For about a month near summer solstice and winter solstice the ISS is in perpetual sunlight. This creates one long visible pass, from just after sunset to just before sunrise, that can be observed by partners on different continents.

All pertinent information about the ISS is available at Heavens-Above.comOnce a team is set up, if only one member sees the pass because the other player or players were clouded out, the one that did make the observation will still be able to create a Waymark if that participant states why the other participant didn’t see the Station. Please also state the other player’s name and approximate location. The ISS Waymark owner may also post a “Visit” log on his partner’s Waymark. If there are more than two creating Waymarks for a single pass, only one visit is allowed and that visit is to be posted on the nearest partner’s Waymark for that pass.

To find a partner you can use Heavens-Above to get Ground Track information and see where the ISS is going. The ground track indicates all points along which the ISS will be seen to fly overhead.

Theoretically, several players could see the ISS pass over one after the other.

Still not sure how to play? Detailed instructions, in text after the double line "============" below will take you step-by-step through the process.

This challenge will require planning ahead since the ISS does not continuously fly over any one area. Be prepared, clouds (or even a forgetful mind) may spoil even the best well planned attempt. For that reason, you may want to plan on observing more than one event with other players.

What You Need To Create A Waymark In This Category, Including The Data That Needs To Be Shared Between Members Of The Group.

(1) Each participant will have to see the ISS at 45° altitude or higher.  The maximum altitude at successive locations must occur at least one minute apart.  (See special rules at the bottom of the page for participants living at or above 55° N or at or below 55° S.)

(2) Naming your waymark:

A list of the cities nearest to each observation site in the order that the pass occurred. Make sure to include your “site number” (like Site 2) in the sequence. For example….

ISS sighting - Pierre, SD – Waterloo, IA – Nashville, TN – Site 1

ISS sighting - Pierre, SD – Waterloo, IA – Nashville, TN – Site 2

ISS sighting - Pierre, SD – Waterloo, IA – Nashville, TN – Site 3


(3) Here is what you need for the Quick Description.

A list of the username of each of the players involved in the order of their sites. For example….

Coyotes, Lycan, and Country Singer sighted the ISS during one pass on January 3, 2007.

(4) Here is what you need for the Long Description.

For EACH site you will need to list the following information (1) The time of maximum altitude. (2) The maximum altitude. (3) The predicted magnitude. (4) The distances covered by the ISS between sites consecutively. To calculate, use the time of Max Altitude for each location. Each full minute = 293 miles (480km). (5) The total time of travel between all sites. (6) The local sky conditions. (7) Your story, e.g. what you experienced and learned etc. (8) A photo or a screen shot of the Ground Track is required. Be sure it shows the date of the Pass. If you choose to take a time elapsed photo of the ISS pass through the night sky, you may post it as the required photo and take pride for being one of few who do.

Your Long Description should look something like this….

At 16:51:32 MST the ISS reached an altitude of 82° and a magnitude of -3.8 over Pierre, SD. At 17:53:04 CST it reached an altitude of 67° and a magnitude of -3.7 over Waterloo, IA. At 17:54:59 CST it reached an altitude of 62° and a magnitude of -3.6 over Nashville, TN.

Pierre is 449 miles from Waterloo. (The difference between 16:51:32 MST and 17:53:04 CST is one minute 32 seconds, times 293 miles/min. equals a distance of 449 miles.) 

Waterloo is 562 miles from Nashville. The total distance covered was 1,011 miles.

The time the ISS took to travel the whole distance was 3 min 27 sec.

The sky in Pierre was clear. The sky in Waterloo was partly cloudy. The sky in Nashville was slightly hazy.

Then post any personal information about your observation.

*Special rules for the far north and far south observers:

For any locations beginning with 55° or 56° N/S latitude, the ISS only needs to make it to a maximum altitude of 30°, not 45°. All places closer to the equator need at least a 45° pass.

For any locations beginning with 57° or 58° N/S latitude, the ISS only needs to make it to a maximum altitude of 25°.

For any locations beginning with 59° or 60° N/S latitude, the ISS only needs to make it to a maximum altitude of 15°.

For any locations beginning with 61° N/S latitude or more, the ISS only needs to make it to a maximum altitude of 10°.  At some latitudes the ISS will never be observable.

Visit requirements:

Listed below are the latest Visitation Rules for the ISS Sightings Game. Simply read the steps beginning with both number ones and go to whatever step it tells you to go to next.

1 You observed a community pass (distance is irrelevant in this case) Go to 2.

1 You observed a pass that has no waymark established. Go to 6.

2 You already own an ISS waymark. Go to 5

2 You do not own an ISS waymark. Go to 3

3 The ISS passed over your location at or above the minimum altitude requirement. Go to 4

3 The ISS passed over your location under the minimum altitude requirement. Go to 6

4 Feel free to make a visit to the nearest waymark established for the community pass you also observed. You must list (1) the date, (2) the time of your local maximum altitude, (3) your maximum local altitude and (4) upload a Heavens-Above image of the ground track past you position. NOTE! If you have a GPSr and a digital camera, please post a photograph of your GPSr next to the printed ground track image. Take the picture at the location from where the observation was made.

5 No matter what the altitude of your pass you may visit the nearest waymark made for a community pass that you also observed. See 4 above for more details.

6 Sorry but you cannot claim a visit.


Link to post

Detailed, step-by-step instructions currently included in the ISS Sighting category description:


In case you need them here are the detailed step by step instructions as promised. 

(1) Go to Heavens-Above.com. Click on “Change your observation location.”  In “Enter place to search for” enter your Town, State and click on “Search.” The map will show your location. If it is correct, scroll down below the map and click on “Update.” You will now be put on the home page.

(2) Once you arrive at the Heavens-Above home page, about 5 lines under Satellites click on the ISS link.

(3) You will now see a chart with all the visible ISS Passes. Look for a pass that is at least 45° Alt. at its Highest point at the top center of the chart. If no passes show or none are above 45°, above the chart you will see a left and right arrow in squares. Click on the right arrow and the chart for the next 10 days will appear. You may have to click on the “Next” link a few times to find a suitable pass. All times are listed in military time. Once found, note the date and time and write it down, copy it, or save a shortcut to it. You’ll need that time and date info later.

(4) Once you find a good pass with a maximum altitude of at least 45 degrees above your horizon, in the details table click on the blue date. Make sure to save the link!

(5) Now click on the Ground Track link located in the upper leftright corner of the Visible Pass Details page. Save the link! [Not important for this challenge is the light colored area shown there. It indicates the area in which the ISS can pass and still be visible from your location at 10° altitude or more. It’s a large area! If the astronauts were in the center of that, the perimeter would be the limit of how far out they could see. They can never see farther north or south than about 70°.(We can’t confirm this.)]

(6) The coordinate lines shown on the Ground track are in 10 degree increments. Follow the ground track toward an area that shows a solid line and find a spot that is at least one minute ISS travel time away from you. (A dotted line means the ISS is in the Earth’s shadow.) For evening passes it’s usually better to look for someone west of you rather than east of you.

(7) From your study of the ground track estimate the coordinate for a good place for site 2. MAKE SURE TO GIVE ALL WEST LONGITUDES A “–” SIGN. Any place along the ground track will have a very high pass. It’s simpler to pick a latitude or longitude along the line, like 100° W then than to estimate the other coordinate between the lines, like 43° N.

(8) Once you choose a coordinate for site 2, go back to the “ISS - Visible Passes” page that you were at earlier.

(9) Once there, look at the URL displayed in the address bar along the top of your screen. Find the coordinate in the URL. I made it red in the following example of Cedar Falls:

http://www.heavens-above.com/main.asp?Loc=Cedar+Falls&Lat=42.528&Lng=-92.445&Alt=271&TZ=CST. Edit the coordinate for the new site. If you like, edit the name of the new location too. Finally, if you know that the time zone for the new location is different, make sure to correct it! It’s listed at the end of the URL. For example, CST stands for Central Standard Time.

(10) Now click your keyboard Enter button. Is your new location close to the ground track? If it isn’t, make the necessary adjustments in the coord in the URL and try again. Once you get it right, click on the Heavens-Above icon on the upper left of the webpage. You will need to go to the “ISS - Visible Passes” info and find the same pass that you yourself hope to see. Not counting a change in time zones, it’ll probably be within four minutes of yours. Remember, the other person should also have a high pass! If your pass is not listed at the other location, then the one you chose is probably too close to the time of sunrise or sunset there. Save your final links.

(12) To find a person to collaborate with go to the Tools for Finding and Hiding Caches page and enter the coordinate you came up with.

(13) Find what looks to be a player that has more than one cache in the area and go to their profile. Do they look promising? If they do, use geocaching.com to go to a cache near the coordinate of site 2. If you suspect a change in time zone you will need to see if they will see the ISS pass an “hour earlier or later than you” by using the map facilities on the cache webpage to locate a city in the same time zone as where the cache is located. Assuming they live near that town go back to Heavens-Above and enter the name of the town there. If it’s listed look up the pass again and save the link! Note to see if the time zone (UTC offset) is different than for your place.

(14) Prepare an explanation about what you hope to accomplish by collaborating with them and drop them an e-mail with the URL of where they should be for the best possible pass. Include the links for both their pass and yours. If they agree to go for it, cross your fingers and hope for the best. Make sure they know the rules and good luck!

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29 minutes ago, vulture1957 said:

oh, and it should say somewhere that the determining factor for deciding 1 minute before or after is the Max Alt time from Heavens Above.


Good point. I thought that was specified but I cannot locate it. 

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16 hours ago, Max and 99 said:

Good point. I thought that was specified but I cannot locate it. 

that's why I mentioned it. I had a few burps trying to do my first ones because of that. Makes so much sense when you know it, but without knowing, you and I could try to do the same pass -- you say you saw it at the beginning of the flight, I saw it at the end. More than a minute apart. But our Max Alt are equal.


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Speaking of the ISS...

The S.S. Katherine Johnson will arrive on the ISS on Monday. So exciting that it is named after the black NASA mathematician. I highly recommend the movie Hidden Figures, which highlights the accomplishments of some amazing women! It is so good.

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20 hours ago, Max and 99 said:

Speaking of the ISS...

The S.S. Katherine Johnson will arrive on the ISS on Monday. So exciting that it is named after the black NASA mathematician. I highly recommend the movie Hidden Figures, which highlights the accomplishments of some amazing women! It is so good.

Loved that movie. 

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