Content Materials

Linear Motion – Position vs. Time

Real World Data Collection and Analysis

Your next task is to locate a satellite orbiting the earth, collect its motion data, and model its motion using a spread sheet in addition to the other representational tools you’ve been exploring.

Go to one of these sites and record the satellite’s latitude, longitude, altitude, and time for a period of 5 minutes (both pages automatically update every minute)

Hubble Space Telescope

International Space Station

Here’s an example of what the Space Station page looks like:

Tracking / Sighting / Other
J-Track / J-Track 3D / Station / Shuttle / More / J-Pass / J-Pass E-Mail / FAQ / Links
16 Jun 2004 19:35 UTC / Current Station Location
Latitude
(Degrees) / Longitude
(Degrees) / Altitude
(Kilometers)
-12.6 / 118.3 / 363.1
Latest Science News
Mob Rules - 6/16/2004
An experiment onboard the International Space Station is helping physicists decipher the group behavior of atoms and molecules.
·  Bacterial Integrated Circuits - 6/10/2004
·  The Transit of Venus: North American Viewer's Guide - 6/2/2004
·  James Cook and the Transit of Venus - 5/28/2004
/
Subscribe for Science@NASA updates / Updates once per minute

By the way, positive latitudes are North and positive longitudes are East. So, extracting the important (for us) information from these data, here are some representative data:

Time (hr:min) / Latitude ( º ) / Longitude ( º ) / Altitude (km)
17:33 / 33.9 S / 11.5 E / 367.4
17:34 / 36.5 S / 14.9 E / 368.4
17:35 / 39.0 S / 18.5 E / 369.5
17:36 / 41.2 S / 22.4 E / 370.5
17:37 / 43.1 S / 26.4 E / 371.4

Now, go to this website to figure out how far the space station traveled during each interval. By the way, these measurements are ground-based. The actual distance traveled by the station would actually be roughly 6% further.

How Far Is It?

Time
(min) / Latitude
(degrees) / Longitude
(degrees) / Interval
Distance (km) / Total
Distance (km)
0 / 33.9 S / 11.5 E / 0 / 0
1 / 36.5 S / 14.9 E / 423 / 423
2 / 39.0 S / 18.5 E / 421 / 844
3 / 41.2 S / 22.4 E / 413 / 1254
4 / 43.1 S / 26.4 E / 392 / 1646

Using Microsoft Excel, here is an X-Y graph of the time and total distance data:

As you can see, the slope of this line is fairly constant, indicating that the space station moved at fairly constant speed. If we select a data point on the graph, add a trendline, and display the equation for the line, we get:

The slope of this line indicates the average speed of the International Space Station is 415 km/min. This is equivalent to roughly 7000 m/s, 15,500 mph or 4.3 mi/s of ground speed. At 370 km, the speed would be closer to 7500 m/s. We are ignoring the fact that the space station (and the Hubble) change altitude somewhat during these few minutes. However, it only changes by roughly 1%, so that’s a pretty safe assumption.

As an interesting side note, we can calculate the speed required for the space station to maintain an orbit at that altitude using the relationship where G = 6.67x10-11 N*m2/kg2, Me=6.0x1024kg, Re=6.4x106m and the altitude h=3.7x105m. This gives us a value closer to 7700 m/s, but that’s pretty close (less than 3% difference).