Measurement	Io	Europa	Ganymede	Callisto
1	2.63 E	4.52W	7.48E	4.07E
2	1.83W	2.13W	6.58E	6.33E
3	1.88W	1.90E	4.43E	8.45E
4	2.62E	4.58E	1.47E	10.20E
5	.83E	3.95E	4.80W	11.55E
6	2.93W	.55E	4.72W	12.55E
7	N/A (Io behind Jupiter)	3.28W	6.75W	13.15E
8	2.90E	4.55W	7.45W	13.25E
9	N/A (Cloudy)	N/A (Cloudy)	N/A (Cloudy)	N/A (Cloudy)
10	2.20W	1.48E	4.88W	12.20E
11	2.38E	4.42E	2.02W	10.95E
12	1.23E	4.22E	N/A	9.35E
13	1.88W	1.92E	4.43E	8.40E
14	.82E	3.95E	1.82W	11.50E
15	N/A	3.25W	6.65W	13.15E
16	1.50W	2.48W	6.85W	12.90E
17	2.42E	4.40E	2.02W	10.95E
18	2.85W	1.02E	4.25E	7.45E

• Collecting data is only half of the lab. To complete a lab, you must also plot to analyze data and draw conclusions via mathematical calculations. To remind you again, our goal is to determine the mass of Jupiter using Kepler's Third Law (please review the Introduction and Objectives page for details). In order to do that, we need to find the orbital period (p) and orbital radius (a) of Jupiter's moons. Unfortunately, you won't be able to found them by just examining the numbers in your data table. You have to first plot the data into points (such as the little dots shown in the figure below), then you will trace a uniform wave along these data points (such as the wave line along the data points in the figure below).

• the vertical coordinate represents the position of the moon as viewed by us through a telescope. Since ours is only a side view, a moon, bounded by its orbit, appears to move between an eastmost and a westmost position about Jupiter. Zero is in the middle, going down we use negative numbers when a moon is east of Jupiter; going up, we use positive numbers when a moon is west of Jupiter.
• the horizontal coordinate marks the number of observation. In your data table, you should already have 18 observations made. Please pay special attention to how the 1/4 period, 1/2 period, and one whole period is determined in the graph. A whole period of the wave is the days it takes from one valley to the next valley (or from one peak to the next peak). 1/2 period is from one zero position point to the next zero positive points. 1/4 period is from a zero position point to the next peak or the next valley.

Now, are you ready to plot your data?

(you have to plot all 4 on separate graphs