Table of Contents

The International Space Station in orbit (ISS)

Specs

 

Countries - Canada, Belgium, Brazil, Denmark, France, Germany, Italy, Japan, the Netherlands, Norway, Russia, Spain, Sweden, Switzerland, the United Kingdom, the United States

Definitions

Orbital Elements

 

Activities

Junior High or High School

• Have the students trace out a ground track of the ISS orbit (between 51.6^o N and 51.6^o S) on a map. An example of the track on a Mercator Projection is given in the student handout. Because a map is not a three-dimensional projection of the Earth, the track will be an S-curve. Also, the altitude of the ISS will not be represented.

• Compare these two-dimensional representations to a track mapped out on a globe.

• Tie a string around the globe (again, between 51.6^o N and 51.6^o S). This will represent the inclination of the ISS as it orbits around the Earth. Also, the width of the string could adequately represent the altitude of the ISS (the scale is about right).

High School

• Have the students figure out why the ISS can be seen from higher latitudes if its altitude is increased. This concept is illustrated in the student handout (pgs. 2 and 3). In this illustration, we can see that the horizon is tangent to your point of latitude. (You can scale your own Earth from a full Earth, a half, a quadrant, etc.).

• Have the students draw lines from the centre of a scaled Earth at angles representing their latitudes, the ISS inclination latitude, and other latitudes. All lines (except for the ISS line) should end at the surface of the Earth.

• Have them extend the ISS line above the surface to a 400 km altitude (based on your scale). The ISS, then, will be a point at the tip of this line.

• Next, have the students draw tangent lines to the points of all the angled lines, as in the illustration. These lines will be the horizons for each latitude. If the ISS (the tip of the point on the 51.6^o line) falls below the horizon lines, it will not be seen. If it is above, it will.

Expand on this activity

Having the students create an illustration like the one below will help them ascertain the altitude the ISS would need to be seen at latitudes outside its inclination limitations. The students can pick a latitude, follow the same procedures of drawing tangent lines, and find the length the hypotenuse line “H” (being the ISS line) would have to be to just meet with the horizon line for that latitude. The altitude at which the ISS would need to be to be seen at that latitude would have to be slightly greater than the length of “H”.

Example

If an observer is at 80^o N, what altitude would the ISS have to be for the observer to see it?

In this case, we are looking at the inner triangle B, D, H in the diagram below. We know the length of B (Earth’s radius) and the angle of A (angle of B (80^o) - angle of line H (51.6^o). We also know the angle of P (180^o - (A + M)). Given the angle of P and the length of B, we can find the length of D (tan P =opposite (B) / adjacent (D)). Once we know the length of D, we can use it and B to find the length of H (Pythagorean). The length of H minus the length B (Earth’s radius) will equal E - the altitude at which the ISS would have to be to just meet the 80^o horizon. So, anything greater than this number would put the altitude right over the horizon to be seen at 80^o N or S.

Example – ISS visibility at 80° N (or S)