A spacecraft is a machine or a vehicle designed in a special way to fly into space beyond earth’s atmosphere for operations. Mostly, they are used for various reasons which include, earth observing, navigation, transport for cargo and humans, communications, planetary explorations and space colonization. Spacecraft can be classified as either orbital or suborbital spaceflight. Orbital spaceflight enters a closed loop orbit around the celestial bodies or around the earth while sub-orbit spaceflight enters the space and finally returns to earth’s surface.
The Galileo spacecraft mission to Jupiter is chosen. This spacecraft was funded by the Federal Republic of Germany and the United States of America. The lead engineer of Galileo project was John Casani. Galileo was built by jet propulsion laboratory located in Germany. The propulsion mode was supplied by Germany. On 18th, October, 1983 the spacecraft was launched at Kennedy Space Center. The mission was completed on 21st September 2003.Its first voyage took it to Venus, from Venus to two asteroids, again back to planet Earth and lastly to its final destination which was Jupiter. This spacecraft was unmanned; the main mission of this project was to study Jupiter and its moons, as well as observing solar system bodies.
During the launching, the probe and orbiter both combined had a mass of 5,653 pounds (2564 kilograms) and which was seven meters high. To keep the spacecraft stable, Galileo had a section that rotated at three revolutions per minute; moreover, six instruments for gathering data were fixed on this section. Antennas were used to propagate information on periodic intervals.
The propulsion design was made up by a subsystem that had 400 N main engine and 12 ten Newton’s thrusters, propellant, and pressurizing tanks of the required plumbing. The combustion system was served by nitrogen tetroxide and monomethylhydrazine fuel which was almost 1000kg. The pressurant used was helium stored in two tanks each weighing 7 kg. Solar panels could not be used as the source of power due to the large distance between Jupiter and sun; likewise, it was impossible to use chemical batteries due to limitations in technology. 500 watts of plutonium power was used to power the spacecraft. The thermoelectric generator was used for decaying radioactive plutonium-238. The heat generated during the decay process was converted to electricity. The process of the solid state see Beck effect would convert heat to electric. The main merits of this process are that long lasting and reliable electricity was generated which would not be affected by the high radiation fields and cold temperatures.
Software’s having 0.65 million lines of programming were being used in sequence design; 1.615m lines in the interpretation of the telemetry and lastly 0.55m lines of code in navigating. Camera systems were contained in the despun sections. These cameras had a very high-resolution power. The Galileo was the only spacecraft to ever utilize charge coupled device. The materials that were used to make the spacecraft were lightweight and strong. It’s lightweight helped to minimize fuel consumption required to reach the orbit. The materials used to make the spacecraft had to be strong so that the craft would be able to withstand the high pressures acting on it.
Another design feature of the probe is that it had 6 RCA 1802 microprocessor CPUs. These units were the one that was controlling the machine. There were six microprocessors two on the despun side and four on the spun side. Memory was also available for storing sequences and for containing buffers for telemetry data and communication in the interbus. Modules in the craft which contained eighteen separate sources of heat were designed such that they would survive a range of accidents. Some of the accidents that the module would survive were during the launch explosion, post impact situations, and re-entry into the atmosphere followed by water or land impact. Graphite was used to make the outer cover was to provide protection against thermal, structural, and eroding environments. The presence of magnetometer which used two sets of sensors allowing the orthogonal components of the magnetic field section to be determined. Lastly, the fuel cell cladding was iridium which provided the cells with post-impact containment.
While taking the measurements, there was some potential for an error occurring from the twisting or bending of magnetometer boom. To take care of these errors, a calibration coil was rigidly mounted on the craft to create reference magnetic field while calibrating.
The spacecraft measuring instruments identified Jupiter’s enormous magnetosphere. Magnetosphere is the region in space, where planets magnetic field control. The instruments also recorded an area of intense radiation. Galileo was the first to observe ammonia clouds in another planet atmosphere. Ammonia particles are created in the atmosphere from materials originating from lower depths.
Measuring instruments also recorded that on moon’s surface there are more widespread volcanic activities as compared to those found on Earth. The information gathered justifies the theory of liquid sea under the icy face of Europa.
Johnson, Torrence V. “The Galileo Mission To Jupiter And Its Moons”. Sci Am 282.2 (2000): 40-49. Web.