Deep Space spacecraft from the USA, Europe and India are all pressing through their mission milestones. India’s Mars Orbiter Mission (MOM) is less than a month away from her arrival at Mars, while NASA’s New Horizons has crossed Nepture’s orbit, en route to Pluto. ESA’s Rosetta mission also announced the shortlisting of landing sites on Comet 67P for the robotic lander, Philae.
While humanity has remained restricted to the realm of Low Earth Orbit (LEO) since the 1970s, multiple robotic spacecraft have continued to extend our reach throughout the solar system.
The two NASA Voyager spacecraft are the long distance explorers, with Voyager 1 now exploring the unknowns of interstellar space.
The United States leads the way in deep space exploration, with a multitude of spacecraft having ventured out into the depths of the solar system, providing vital data for scientists, along with beaming back spectacular photography of our planetary neighbors.
One such spacecraft is closing in on her primary destination, as NASA’s New Horizons mission continues to blaze a path toward Pluto.
New Horizons began her journey atop of an Atlas V rocket in 2006, sent directly into an Earth-and-solar-escape trajectory with an Earth-relative speed of 36,373 mph – setting a record for the highest velocity of a human-made object from Earth.
A Jupiter flyby provided a gravitational assist, increasing New Horizon’s velocity by another 9,000 mph.
On Monday, NASA noted New Horizons had reached Neptune’s orbit – nearly 2.75 billion miles from Earth – in a record eight years and eight months.
New Horizons’ milestone matches precisely the 25th anniversary of the historic encounter of NASA’s Voyager 2 spacecraft with Neptune on August 25, 1989.
“NASA’s Voyager 1 and 2 explored the entire middle zone of the solar system where the giant planets orbit,” noted Alan Stern, New Horizons principal investigator at the Southwest Research Institute in Boulder, Colorado.
“Now we stand on Voyager’s broad shoulders to explore the even more distant and mysterious Pluto system.”
When New Horizons arrives at Pluto for her closest approach on 14 July 2015, she will not only explore Pluto and its neighbors Charon, Nix, and Hydra, but also two newly named moons which were discovered in 2011 and 2012 via the Hubble Space Telescope.
The planned search will involve targeting a small area of sky in search of a Kuiper Belt object (KBO) for the outbound spacecraft to visit. The Kuiper Belt – a vast debris field of icy bodies – was formed from the solar system’s formation 4.6 billion years ago.
Hubble will scan an area of sky in the direction of the constellation Sagittarius to try and identify any objects orbiting within the Kuiper Belt.
“No country except the United States has the demonstrated capability to explore so far away,” Dr. Stern added.
“The U.S. has led the exploration of the planets and space to a degree no other nation has, and continues to do so with New Horizons.
“We’re incredibly proud that New Horizons represents the nation again as NASA breaks records with its newest, farthest and very capable planetary exploration spacecraft.”
NASA’s dominance in exploring the solar system is mirrored by its success in sending spacecraft to the specific destination of Mars. However, India is hoping the Mars Orbiter Mission (MOM) will set them on a path towards the Red Planet.
MOM – launched via a PSLV rocket in November, 2013 – is based on a derivative of ISRO’s I-1K satellite bus, a platform first used for the METSAT-1 weather satellite launched in September 2002.
The MOM spacecraft hosts five scientific instruments: the Mars Color Camera; Thermal Infrared Imaging Spectrometer; Lyman Alpha Photometer; Methane Sensor for Mars and Mars Exospheric Neutral Composition Analyser.
Set to arrive in an areocentric orbit on 24 September, MOM will make India the first Asian country to have a spacecraft orbiting the red planet. Japan and China have both attempted missions to Mars; Japan with Nozomi in 2003, and China with Yinghuo-1 in 2011; however both missions failed.
Three orbiters are currently in operation around Mars; NASA’s Mars Odyssey and Mars Reconnaissance Orbiter, and ESA’s Mars Express – soon to be joined by NASA’s MAVEN orbiter. A further two spacecraft are operational on the surface: the Opportunity rover and Curiosity (Mars Science Laboratory).
Another deep space mission – this time under the control of the European Space Agency – is also closing in on the business end of its mission.
The Rosetta mission was launched on March 2, 2004 via an Ariane 5G rocket, ahead of clocking up 6.4 billion kilometers, taking in an orbit of Jupiter and also involved passing by Earth three times and Mars once, while also flying past two asteroids.
Next up will be another milestone, as the lander, Philae, will aim to become only the second human-made object to land on a cosmic body far from Earth. She will follow the Huygens probe that landed on Saturn’s moon Titan, 1.3 billion kilometers from Earth, in January 2005.
Where she will land on the comet is now under evaluation, with a shortlist of five landing sites selected, according to ESA on Monday.
European scientists noted that the landing is expected to take place in mid-November when the comet is about 450 million km from the Sun, before activity on the comet reaches levels that might jeopardise the safe and accurate deployment of Philae to the comet’s surface, and before surface material is modified by this activity.
With an array of close up imagery and data now at hand from the Rosetta spacecraft, the Landing Site Selection Group met in Toulouse, France over the weekend, to consider the available data and determine a shortlist of five candidate sites.
“This is the first time landing sites on a comet have been considered,” noted Stephan Ulamec, Lander Manager at DLR. “Based on the particular shape and the global topography of Comet 67P/ Churyumov-Gerasimenko, it is probably no surprise that many locations had to be ruled out.
“The candidate sites that we want to follow up for further analysis are thought to be technically feasible on the basis of a preliminary analysis of flight dynamics and other key issues – for example they all provide at least six hours of daylight per comet rotation and offer some flat terrain. Of course, every site has the potential for unique scientific discoveries.”
Even before the mission arrived at the comet, scientists knew that the southern regions offered the most stable landing conditions, not least because Philae is powered by solar cells.
The probe will experience higher levels of illumination as the comet approaches the Sun, aiding its health.
The five shortlisted sites were assigned a letter from an original pre-selection of 10 possible sites, which does not signify any ranking.
Three sites (B, I and J) are located on the smaller of the two lobes of the comet and two sites (A and C) are located on the larger lobe.
The Rosetta mission team are working towards a nominal landing date of 11 November.
As such, confirmation of the primary landing site is expected to be decided on 12 October. This will be followed by a formal Go/No Go from ESA, in agreement with the lander team, after a comprehensive readiness review on 14 October.
“The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land,” added Fred Jansen, ESA Rosetta mission manager.
“We had to complete our preliminary analysis on candidate sites very quickly after arriving at the comet, and now we have just a few more weeks to determine the primary site. The clock is ticking and we now have to meet the challenge to pick the best possible landing site.”
(Images via NASA, ISRO and ESA).