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Observe YES2

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ESA / Education / Young Engineers Satellites

The YES2 project has already shown that collaboration in a wide context can produce fantastic results. The contributions in expertise and time from student engineers’ world-wide have created something special in YES2. Now the YES2 team wants you to get involved too.

Once the mission is operational YES2 will be longest structure ever deployed in space. The tether will be visible from Earth in certain places and the team would like your help in documenting this record breaking event, with photo and video evidence.

Visibility details

Launch is scheduled to take place on 14th September 2007 at approximately 11:00 Coordinated Universal Time (UTC), which equates roughly to Greenwich Mean Time (GMT). Once launched, the operational orbit for YES2 is between 250 and 300km above the Earth. It should have a 63° inclination from the equator, once in orbit.

YES2 is scheduled to become operational on the 25th September between 03:00 and 04:00 UTC, with the ejection of the tether beginning between 04:00 and 06:00 UTC.

In the world map above, the red marked zones indicate locations on Earth where the YES2 tether should be visible in the sky, once deployed.

There are some limitations for visibility and these are as follows:

  1. The minimum visible length of deployed tether is 2000m
  2. The minimum elevation for ground observation is 2° above the horizon. This means that on the world map that the edge of the red marked zones, the tether will be visible at about this elevation from the ground. The more inside these areas that you are, the higher in the sky the tether will be.

The tether should be visible from the following locations:

  • South America (below 55°S)
  • Antarctic Peninsula (above 82°S)
  • East Russia and western Alaska (above 170°E)

Visibility examples

The following graphs show the path through the sky that the YES2 tether is likely to follow from the perspective of Anchorage in Alaska, Punta Arenas in Chile and Bellinghausen Station in the Antarctic. Beside is further visibilty window information for both areas.

Punta Arenas

Coordinated Universal Time
Visibility Window: 25 September 2007, 07:09 – 07:11

Local Time (UTC-4h)
Visibility Window: 25 September 2007, 03:09 – 03:11 >
Tether movement: East to West.


Coordinated Universal Time
Visibility Window: 25 September 2007 04:57 – 05:04

Local Time (UTC-9h)
Visibility Window: 24 September 2007, 19:57 – 20:04 >
Tether movement: East to West.

Bellinghausen Station

Coordinated Universal Time
Visibility Window: 25 September 2007, 07:09 – 07:14

Local Time (UTC-4h)
Visibility Window: 25 September 2007, 03:09 – 03:14 >
Tether movement: West to East.

More detailed information

For more experienced observers, below is a table listing all the reference orbital parameters for the YES2 launch.

Launch date: 14 September 2007
Launch time: 11:00 UTC / 14:00 MDT
Launch site: Baikonur: 45.7N, 63.5E
Epoche [UTC]: 14 September 2007, 10:51:37 UTC
SMA [km]: 6656.093
Eccentricity [-]: 0.003
Inclination [°]: 63.010
Angle of Perigee [°]: 51.388
RAAN [°]: 191.027
TA [°]: 308.612
Period [seconds]: 5404.308

This table lists the deployment conditions based on the predicted orbit parameters.

Epoche [UTC]: 04:46:00
SMA [km]: 6656.093
Apogee [km]: 298
Perigee [km]: 258
Inclination [°]: 63.01
RAAN [°]: 148.995
Angle of Perigee [°]: 52.676

Please send all your YES2 deployment pictures and videos to

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