 |
Asia-Pacific Forum
on Science Learning and Teaching, Volume 12, Issue 1, Article 12
(Jun., 2011) |
(Student’s Copy)
Part 1
The satellite Observer, which has been developed to continuously examine the inner structure of the Sun, its external atmosphere, and the formation of solar winds, and transfer the findings to the Earth, has been placed into its orbit somewhere between the Sun and Earth. There were broadcast interruptions after the satellite had broadcasted for 23 days.
What is the problem?
What are the possible causes of the problem? Please propose the hypotheses.
What can be done to solve the problem?
SESSION 1
Part 2
The scientists responsible for putting the Observers into its orbit and make it function are exploring the reasons for the broadcast interruptions. Experts, after all the observation and research they had done, have diagnosed that the problem was not caused by the electromagnetic waves emitted from the Sun. Moreover, it was confirmed that no meteor or comet passed by on the date the interruptions started. The experts have come to an agreement on checking the electronic components of the satellite, revising all the computations concerning the Observer, and the positions of the planets and satellites.
Summarize the information given above.
Reevaluate your initial hypotheses in the light of the new information.
What is the effect of the positions of the planets and satellites on the Observer?
SESSION 1
Part 3
The electronic components of the Observer have been checked by experts, and no problem has been diagnosed. They have explained that the change in the position of the Moon has changed the gravitational force affecting the Observer, and that might be the reason for its having veered of its course.
What is gravity?
What laws of physics might gravitational force relate to?
How are the orbital motions of the Observer and Moon?
What are the physical quantities concerning the orbital motions of the Observer and Moon?
What do you need to know/learn?
Part 1
Observer moves around the Sun in step with the Earth, by slowly orbiting around the First Lagrangian Point (L1), where the combined gravity of the Earth and Sun keep SOHO in an orbit locked to the Earth-Sun line (See Fig. 1). The L1 point is approximately 1.5 million kilometers away from Earth (about four times the distance of the Moon), in the direction of the Sun. The experts who have examined the other satellite records have found out that the Moon has come on the route of Sun-Earth 23 days after the Observer had been put into its orbit. They have also specified that the Observer is 7,16.105 km far away from the Moon. It is assumed that this change in the position of the Moon might have altered the orbital parameters of the Observer. Therefore, the orbital velocity of the Observer around the Sun and its orbital period have been recomputed.
Figure 1. The first orbital look of the Observer (the figure has not been scaled)
Calculate the orbital speed and orbital period of the Observer when it is in circular orbit around the Sun considering its first look.
[Distance to the Sun-Earth (r): take 1,5.108km, Me=6.1024 kg, Ms=2. 1030 kg
G=6,67.10-11m3.kg-1.s2 .]
Figure 2. The orbital look of the Observer 23 days later (the figure has not been scaled)
Assuming that 23 days later, the Observer will be revolving around the Sun only in circular orbit, compute its orbital speed and orbital period. (See Fig. 2)
Distance to the Moon and Earth: 3,84.105 km, Mm=7,35.1022 kg
Compare the two orbital speeds and orbital periods. Interpret the findings.
SESSION 2
Part 2
The experts having studied the satellite records and computed the orbital speed and orbital period of the Observer have come to the conclusion that it got closer to the Earth; its orbital speed decreased, but its orbital period increased as a consequence of the gravitation of the Moon. The experts have quantized the required energy for putting the Observer, which has veered off course, into its old orbit, and they have stated that it is sufficient. After all the discussions concerning the situation of the Observer, the scientists have agreed that it had to be put into its old orbit, and that as the orbit around L1 is tentative, they should apply “station-keeping maneuvre” strategy periodically. The experts have decided that the orbital entry point of the Observer, which moves anticlockwise, should be the point where the tangent line extending from the Observer’s location to the elliptical orbit intersects the ellipse, and so they have started doing the necessary calculations.
Summarize the information given.
While putting the Observer into its old orbit, what mathematical input will be used?
What do you need to know/learn?
Part 1
The experts know that when the Observer was veering off course, it moved along the axis between the Sun and Earth; moved 2.105 km closer from point M, which is located on the old orbit, to the Earth; and that the orbital motion changed merely in circular motion around the Sun. They believe that, in order to put the Observer into its old orbit, the rockets should be started by using the fuel in the energy tanks. They have also decided that the orbital entry point of the Observer, which moves anticlockwise, should be the point where the tangent line extending from the Observer’s location (point N) to the elliptical orbit intersects the ellipse, and they have done the necessary calculations (see Fig. 3). As a result, they have determined the coordinates of the location where the Observer will go into its old orbit.
Figure 3. The upper view of the Observer’s location (the figure has not been scaled)
Summarize the given information.
Determine the coordinates where the Observer will be put into its old orbit.
(the semimajor axis distances of the old elliptical orbit of the Observer around point L1 are a=6,5.105 km, b=2.105 km)
SESSION 3
Part 2 (FINAL)
Summarize all the activities carried out upto this session, and write the learning objectives for every session.
