Sample Astronomy Paper on The Rosetta Mission
Abstract
The Rosetta mission is known, especially among scientists and engineers, as one of the most daring missions undertaken by humanity, in the sense that it was the first space mission to explore a comet. It managed to surmount all challenges, from its launch, through its maneuvers across the inner solar system, to its successful capture in orbit of a comet. The mission would have been a complete success had the spacecraft and its lander not experienced power supply problems.
A fairly comprehensive account of the Rosetta mission – from Rosetta’s launch to the abortion of the mission – is provided in its entirety in this paper. Information is sourced from NASA’s website and other websites that were specifically set up to keep track of the Rosetta mission.
- Introduction
Rosetta was a space probe that was built and launched by the European Space Agency (or EPA) in 2004, alongside its lander module, Philae, with the purpose of studying comet 67P. It took a decade after its launch to reach its target comet, making it the first spacecraft to revolve around a comet (“Latest News” par. 17). To accomplish this feat, Rosetta had to perform numerous maneuvers of a number of asteroid and other objects on its path during its flight. These successful maneuvers were hailed as a demonstration of the European Space Agency’s sophistication in space science control and instrumentation. But even more impressive was the successful capture of the Rosetta Spacecraft in orbit of its target comet.
The Rosetta space probe was named after a Steele originating in Egypt and featuring a triple-script decree, called the Rosetta stone. On the other hand, the Philae, its lander, gets its name from the Philae obelisk, which bears hieroglyphic inscriptions in both Egyptian and Greek languages. The naming of the space probe and its lander as such was motivated by the fact that a comparison of the hieroglyphs made it easier and faster to decipher the writing system of ancient Egypt: It was hoped that the Rosetta Space probe and its Philae Lander would similarly make it easier to unravel the mysteries of the comets and the wider solar system.
- About Rosetta
Rosetta’s design was such as to successfully accomplish maneuvers of asteroids and bodies on its path, and finally be successfully captured in orbit, around the target comet. At the centre of the spacecrafts propulsion system were twenty four pairs of bi-propellant thruster, each thruster being capable of generating ten-Newtons of force. Rosetta made use of both fuel and gravity assist to successfully achieve these maneuvers.
The Rosetta mission was viewed as a cornerstone mission, in the sense that it was going to be the first to be involved in such a mission. What was special about the Rosetta mission was that no other space mission had been involved in the exploration of a comet. An exploration of any comet would greatly contribute to our understanding not just of comets, but the formation and the evolution of the solar system as a whole.
The Rosetta space probe is fairly large in volume and massive. The dimensions of its central frame and platform of are 2.8m by 2.1m by 2.8, while it has an estimated mass of three tons, part of which is the 100Kg of the 165Kg of instrumentation (“Latest News” par. 16). The space probe’s communication system is comprised of steerable dish antenna and a fixed antenna.
The Rosetta space probe was put together in such a way as to optimize its operation and therefore accomplish the mission for which it was designed. The payload, which shelters the probe’s instruments, was mounted on the upper part of the spacecraft, while the bus module, which houses the probes support systems, was attached to the underside of the probe. The Rosetta spacecraft also had heaters attached around it to maintain the operational temperature of its systems at the optimal when the spacecraft was too far from the sun to be warmed enough by the sun’s heat.
Pertaining to power supply, the Rosetta was almost totally reliant on solar energy. To harness solar energy, the spacecraft made use of two solar arrays. Rosetta’s solar power supply was designed to generate a maximum of 1.5KW, and that was to be achieved when the comet the spacecraft would be orbiting was closest to the sun; a 400 Watt minimum when the probe was hibernating; and 850 Watts at the start of the comet’s operation (“Latest News” par. 16).
- The Total Trip – Launch and Maneuver
Rosetta had been initially scheduled to be launched on the 12th of January 2003 to meet in 2011 with comet 46P, but things did not go according to plan. The launch was postponed when a carrier rocket, Ariane 5, failed during the launch of Hot Bird 7 on the 11th of December 2002. The Rosetta had to be grounded for the period of the determination of the source of Ariane 5’s failure.
Upon the failure having been determined and the necessary corrections made, Rosetta’s launch was rescheduled not just to take place another time, but also to meet at that time with a different comet. The new target comet was comet 67P, and the spacecraft was scheduled to meet it in 2014. Comet 67P had a larger mass and a higher impact velocity compared to the initial comet, creating a requirement for that the probe’s landing gear be modified. Comet 67P (also known as Churyumov-Gerasimenko) has a maximum velocity of 38Km per second, measures 4.3Km by 4.1Km, takes 6.45 years to complete one cycle of its orbit, and 12.4 hours to complete a rotation about its axis. The Rosetta space probe was finally launched from the Guiana Space Centre at 07:17 UTC on the 2nd of March 2004.
One of the requirements for a successful capture of the Rosetta spacecraft in orbit of its target comet was sufficient velocity to make it happen. To acquire this velocity, the Rosetta probe exploited gravity assist for its acceleration and maneuver about the inner solar system (“Rosetta – ESA’s Comet Chaser” par. 4). The orbit of the target comet already been predicted by the European Space Agency’s scientists to a reasonably good accuracy. During its flight, instrumentation onboard the Rosetta were used to reduce the margin of error in the orbital position of the comet.
Rosetta was scheduled to fly by Mars’ low altitude on the 25th of February 2007 to make a correction on its trajectory, notwithstanding the risk of collision with the planet as the altitude was approximately very low. During the spacecrafts rendezvous with the planet, the solar panels were rendered redundant as the planet eclipsed them from the sun for a quarter an hour, resulting in a concerning shortage in the supply of power. As a result, the Rosetta was forced into hibernation, cutting of communication and powering its flight with batteries which had not been intended for that use (“Rosetta – ESA’s Comet Chaser” par. 6). Fortunately, the mass flyby turned out to be a success, with the spacecraft even taking and sending to earth fine image of the Martian atmosphere and surface.
The spacecraft first flew by the Earth on the 4th of March 2005, before its encounter with Mars, and flew by the Earth for the second time on the 13th of November 2007. Interesting about this second flyby is that the spacecraft was initially mistaken for an asteroid but was found out to be the Rosetta when the trajectory of the supposed asteroid was recognized to resemble that of the Rosetta (“Rosetta – ESA’s Comet Chaser” par. 9).
On the 5th of September 2008, the spacecraft flew by the 2867 Šteins asteroid, with the spacecraft’s cameras being used to tune its trajectory to a safe separation from the asteroid. Other instruments on the Rosetta measured the asteroid as well, after which it later flew by the Earth for the third and final time on 12th of November 2009.
Rosetta’s last flyby was that of the asteroid 21 Lutetia, and, as a result of the close proximity of the flyby, the Rosetta’s cameras were able to capture detailed images of the asteroid. Other measurements of the asteroid by the spacecraft’s instruments were its plasma environment and magnetic field.
In May 2004, to lower the velocity of Rosetta relative to comet 67P, its main target comet, it started a series burns. Its speed was thus reduced to a value low enough to facilitate its capture in orbit around the comet.
- Rosetta’s Capture and Spacecraft Signal
Rosetta’s encounter with comet 67P happened in August 2014, subsequent to which it performed a series of maneuvers until it finally entered an actual orbit around the comet on the 10th of September the same year (ESA SCIENCE par. 7). Comet 67P is a member of the Jupiter family comets, with and takes 12.4 hours to rotate about its axis, and 6.45 years to complete its orbit (“Hang out with Rosetta” par. 4). The spacecraft mapped its comet in preparation for the detachment of its lander, leading to the determination a potential landing site on the 25th of August.
On 12th November 2014, Rosetta released its lander, the Philae. The Philae’s landing on the comet was not as smooth as would have been hoped for. Upon first making contact with the surface of the comet, it bounced from it twice before settling on it.
On its third contact with the surface of the comet, the Philae fired two harpoons to grip it on the surface of the comet, thus preventing any further potential bouncing. On the surface of the comet, the lander examined the characteristics of the nucleus, the comet’s chemical composition and the evolution of the comet’s activities over time.
The Philae’s landing site was however not suitable. It landed in the shadow of a cliff on the comet, ending up eclipsed from the sun, the result of which was an inadequacy in the supply of solar energy to its solar panels. The Rosetta thus lost contact with the Philae two days after its landing because the batteries on which it relied for its power supply ran out, before much of the observation and data collection could be done (“Hang out with Rosetta” par. 4). Contact with the Philae was made intermittently and only briefly each time, months after the first loss of communication, but when connection was lost again, Rosetta’s transmitter that communicated with the Philae was switched off to save power (“Hang out with Rosetta” par. 4). Images taken by Rosetta later in September 2016 revealed the precise location of the lander.
- Experience, Results and Instruments
The Rosetta mission made a number of discoveries pertinent to comet 67P, three of the most notable ones being the behavior of the magnetic field around the comet, the property of the comet’s water vapor, and the process of degradation of the comet’s carbon dioxide and water.
Rosetta discovered that comet 67P has a magnetic field that oscillates with at a very low frequency. The magnetic field is not however associated with the comet. The landing of the Philae on the nucleus of the comet revealed that the comet does not generate its own magnetic field, leaving the solar wind as the only explanation for the magnetic field detected (“Latest News” par.5).
The comet’s water vapor was discovered to be different from water on earth, with its deuterium to hydrogen ratio being triple that of water found on earth, making it improbable that the Earth may have gotten its water from a collision with a comet (“Latest News” par.4).
Finally, Rosetta discovered that the process of degradation of carbon dioxide and oxygen molecules released by the nucleus of the comet into its coma was due to electrons that were one kilometer above the comet, rather than solar photons as had initially been thought (“Latest News” par.5).
Due to problems with power supply, the Rosetta mission had to be ended prematurely. The prospect of re-hibernating Rosetta to save power was undermined by the lack of assurance that there would be enough power supply to run the heaters of the spacecraft, and thus prevent it from freezing (“Rosetta” par. 1). The decision was therefore taken to make Rosetta land on the comet’s surface, taking measurements and photographs during its fall, the motivation being to maximize the mission’s return.
- Instruments Used
A number of instruments were installed on the comet for the purpose making observations, taking photographs, making measurements, analyzing the data collected and transmitting information between Philae, Rosetta and ESA’s ground station. The following instruments were used by the Rosetta: ALICE, to measure the amount of noble gases on the comet’s nucleus; OSIRIS, to take digital images of the comet; VIRTIS, to take images of the nucleus in the infrared wavelength; MIRO, to measure the temperature and quantity of volatile gases; CONSERT, to extra information about the comet’s interior using radar; and, RSI, to investigate the nucleus using the spacecraft’s information system (“ESA Science and Technology” par. 8).
While the Rosetta had enough instruments to capitalize on the success of the mission and get the optimal amount of scientific information about its target comet, not all these resources were used to their full capacity. The mission was massively undermined by power supply issues resulting landing of the Philae at a position where it was eclipsed from the sun whose energy it was to use to generate electricity.
- Summary and Conclusions
The Rosetta mission was unique, in comparison to other space missions, in the sense that it managed to achieve feats that had not been achieved by previous space missions. The mission’s successful surmounting of a number of space science challenges has highly raised the profile of the European Space Agency, perhaps making NASA worried about its future as the rest of the world’s envy in the fields of space science, space engineering and space exploration.
The Rosetta space probe will always have its place as the first ever space probe to be captured by comet (and to orbit a comet’s nucleus), courtesy of the European Space Agency’s engineering, instrumentation and control technology. The Rosetta space probe’s orbiting of the comet also meant that it had to be in flight alongside the comet as the comet moved in the direction of the inner solar system, making it the first ever spacecraft to do so.
The orbiting of a comet and the flying alongside a comet by the Rosetta space mission were only two of the first ever accomplishments by any space mission so far. The Rosetta probe was the first space probe to examine closely the behavior a frozen comet under the comet’s exposure to the warmth of the sun. Within months of the spacecraft’s orbiting of the comet, the space probe dispatched its lander, the Philae, which successfully landed on the nucleus of the comet, marking the first even artificially controlled landing on a nucleus of any comet. The Philae’s instrumentation was the first to acquire digital images of a comet’s surface, and to make the first ever analysis of the composition of a comet on the comets surface.
During its flight – between its launch and its capture by its target comet – the Rosetta probe made a few first ever maneuvers across the solar system. The Rosetta space probe was the first ever spacecraft to make a passage through the main asteroid belt, and was the first to encounter numerous primitive interplanetary objects. The probe will also be remembered as the first ever to closely fly by the orbit of Jupiter, powered only by solar energy.
Finally, in spite of the problems with power supply, the mission still managed to take measurements and photographs, and gather information about the magnetic field about the comet, the nature of its water, and the process of degradation of carbon dioxide and water.
Taking into consideration the challenges encountered by the mission and the results obtained, the mission was arguably a big success.
Works Cited
ESA Science & Technology: Rosetta. European Space Agency, n.d. Web. 25 Sept. 2016. <http://sci.esa.int/rosetta/>.
“Hang out with Rosetta.” Rosetta / Space Science / Our Activities / ESA. N.p., n.d. Web. 25 Sept. 2016. <http://www.esa.int/Our_Activities/Space_Science/Rosetta>.
“Latest News.” Rosetta | Rendezvous with a Comet. N.p., n.d. Web. 25 Sept. 2016. <http://rosetta.esa.int/>.
“Rosetta – ESA’s Comet Chaser.” Rosetta – ESA’s Comet Chaser. N.p., n.d. Web. 25 Sept. 2016. <http://blogs.esa.int/rosetta/>.
“Rosetta.” Rosetta | International Mission to a Comet, In Search of Our Origins. N.p., n.d. Web. 25 Sept. 2016. <http://rosetta.jpl.nasa.gov/>.