8/12/2019 Soal Pelatnas 1 - Gravity

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Gravity

In the film Gravity, Dr. Ryan Stone and Matt Kowalski conducted a spacewalk to service Hubble

Space Telescope. While at the spacewalk, Russian missile strike on a defunct satellite, caused a

chain reaction forming a cloud of debris in space threatening the spacewalk. The debris struck the

spacewalk team, in the midst of such chaos, Dr. Ryan Stone was separated from Matt Kowalski.

Panicking, Dr. Ryan Stone spinning around away from the Hubble Space Telescope, depleting her

oxygen level to near critical, 10%. Matt Kowalski remained near Hubble Space Telescope, starts

searching Dr. Ryan Stone. To find Dr. Ryan Stone, Matt Kowalski have to observe the star field,

looking for Dr.Ryan’s torchlight. 

While looking toward the opposite of the earth, Matt Kowalski found three strange lights which look

like strange stars. The first one is an bright object with magnitude of about -5 mag, but the object

always disappeared after 3 seconds and appeared again after 3 seconds of disappearance. The

second one, is an object with the magnitude like the first object, what interesting is it ’s  always

remained near the horizon, always moving relative to the background stars and remained in the

same position in Matt Kowalski’s field of view while looking at the western horizon, but after a few

minutes, it disappeared. The third one, a bright star, located at the opposite direction of the sun,

with the same magnitude as Arcturus except it is having yellowish color. Low on jetpack fuel, Matt

Kowalski must pick one of the lights having the highest probability it’s really came from Dr. Ryan’s

torchlight and ultimately reunites with Dr. Ryan. Which one should Matt Kowalski choose? Why?

What the other objects really are?

To be able to reach Dr. Ryan Stone, Matt Kowalski needs to control the thrust from the jetpack by

knowing the distance between them. Determine the distance of the two astronauts given the

situation. 

Reunited with Dr. Ryan, Matt Kowalski have to go to the ISS. ISS is located approximately 1500 m to

the west from the two astronauts. The sun is rising at the moment, determine the surface

brightness of the ISS as seen by Matt Kowalski in mag/arcsec2.

You may use any assumptions if needed.

Known variables:

NASA’s standard space torchlight specs: 40W, yellowish color light LED, fixed to space suit’s helmet. 

NASA’s spacesuit oxygen tank capacity: adequate for 6 hours at normal condition

Hubble Space Telescope orbital period: 96 minutes

ISS orbital period: 93 minutes

ISS size: 72.8 m x 20m x 108.5m

Arcturus’s Apparent Magnitude as seen from space: -0,04