Space Technology

This chapter asks which types of orbit Malaysian satellites use and how many days Dato’ Dr. Sheikh Muszaphar Shukor, the first Malaysian astronaut, spent at the International Space Station (ISS) p. 234. Malaysia is among the first Asian countries to launch a 5G demonstration project, and the Global Satellite Network enables the worldwide transfer of information from one country to another p. 235.

9.1 Satellite

A satellite is an object which orbits planets or stars, and the Moon is a natural satellite which orbits Earth p. 236. Satellite orbits around Earth are grouped into five types according to orbital height (altitude) p. 236. Low Earth Orbit (LEO) has an orbital height of 180 – 2 000 km, Medium Earth Orbit (MEO) 2 000 – 35 780 km, and High Earth Orbit (HEO) equal to or exceeding 35 780 km p. 236. Geosynchronous Orbit (GSO) and Geostationary Orbit (GEO) both have an orbital height of 35 786 km p. 236. The orbital plane of GSO is at an inclined angle to the equatorial plane, while GEO has the equatorial plane as its orbital plane p. 236.

There are two orbital shapes, perfectly circular and elliptical p. 237. GEO is perfectly circular, MEO and HEO are elliptical, and LEO and GSO are perfectly circular or elliptical p. 237. A satellite in an elliptical orbit has two specific positions, apogee and perigee p. 237. The apogee is the position of the satellite which is furthest from the planet or star encircled by the satellite p. 237.

The higher the orbital height of a satellite, the lower the satellite speed for it to remain in orbit p. 237. This is because the gravitational force on a satellite decreases when its orbital height increases p. 237. For example, a HEO satellite at 35 780 km moves at 11 100 km/h, while a LEO satellite at 705 km moves at 27 500 km/h p. 237.

Launch vehicles, made up of one or more rockets, send satellites or spacecrafts into outer space p. 239. A satellite can be placed directly into orbit, or through the Hohmann transfer orbit, with burning at perigee and burning at apogee to move from a small orbit to a large orbit p. 239. Launch vehicles are divided into expendable launch vehicles (ELV) and reusable launch vehicles (RLV) p. 239.

The ISS is the result of efforts from five space agencies, namely NASA (America), Roscosmos (Russia), JAXA (Japan), ESA (Europe) and CSA (Canada) p. 240. Zero gravity is the condition when no significant gravitational force effect is felt, as in indoor skydiving p. 241. In indoor skydiving, the thrust of a very strong upward air flow is equal in value to the participant’s weight but in the opposite direction p. 241. The frequency of the ISS orbiting Earth in a day can be calculated from its orbital height and speed, using the radius of Earth, 6.37 × 10⁶ m p. 241. The position of the ISS can also be tracked with smartphone applications p. 241.

Rapid development in space technology has increased space junk, which includes non-functioning satellites, used parts of ELV, satellite debris from collisions and exhausted rockets p. 242. According to NASA, 95% of thousands of man-made objects in low Earth orbit are space junk, and the more space junk there is, the higher the risk of collision p. 242. The weather satellite GOES normally changes its orbit several times to avoid collision with space junk p. 242. Space technology has also increased research and development in fields such as human health, response to climate change and disasters, global education and the space economy p. 242.

9.2 Global Positioning System (GPS)

Global Positioning System (GPS) is a navigation system which gives information on location and time to its users in all weather conditions p. 243. GPS is made up of three segments, the control segment, space segment and user segment p. 243.

The control segment is made up of a master control station, alternative master control station, command and control antennas and monitor stations p. 244. The antennas send the GPS satellite position, time correction factor for the satellite clock, atmospheric data and almanac to the GPS satellites p. 244. GPS satellites orbit Earth at an orbital height of 20 000 km in a semi-synchronous Earth orbit with an orbital period of about 12 hours p. 244. At least 4 GPS satellites can be seen at an angle of 15° or more from the horizontal axis at any time from all locations on Earth p. 244. A GPS satellite sends its position and the time the signal is sent to the GPS receiving device p. 244.

A GPS user is anyone who uses a GPS receiving device such as a smartphone p. 244. A location can be written in degrees, minutes and seconds (DMS) or decimal degree (DD), for example 5°26’25”N 100°18’32”E for Georgetown, Pulau Pinang p. 244. The National Planetarium, Kuala Lumpur, is at 3°08’22.04”N 101°41’22.53”E in DMS, or 3.139456, 101.689593 in DD p. 245. A positive DD value represents latitude in the northern hemisphere or longitude to the east of the Greenwich Meridian, and a negative value represents the southern hemisphere or the west p. 245.

GPS is used for navigation in land, sea, air and space transport, and Google Maps and Waze are examples of navigation applications that use GPS coordinates p. 246. A car GPS tracker is another device that uses GPS p. 247.