It’s been a busy month spacefans! I hope that you’ve all readjusted back to normality, can remember what day it is and that mince pies and prosecco are no longer acceptable for breakfast. This time we have the latest New Horizons flyby, the Osiris-REx mission reaching its destination, and of course the Chinese Moon landing.
NEW HORIZONS REACHES ULTIMA THULE
The New Horizons mission team has released the first detailed images of the most distant object ever explored, the Kuiper Belt object nicknamed Ultima Thule. Its remarkable appearance, unlike anything we’ve seen before, will give us clues as to the processes that built the planets four and a half billion years ago.
“This flyby is a historic achievement,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Never before has any spacecraft team tracked down such a small body at such high speed so far away in the abyss of space. New Horizons has set a new bar for state-of-the-art spacecraft navigation.”
The new images, taken from as close as 27,000 kilometers on approach — revealed Ultima Thule as a “contact binary,” consisting of two connected spheres. End to end, the world measures 31 kilometer) in length. The team has dubbed the larger sphere “Ultima” 19 kilometers across and the smaller sphere “Thule” 14 kilometers across.
The team says that the two parts of the object most likely joined as early as 99 percent of the way back to the formation of the solar system, coming together at a low speed.
“New Horizons is like a time machine, taking us back to the birth of the solar system. We are seeing a physical representation of the beginning of planetary formation, frozen in time,” said Jeff Moore, New Horizons Geology and Geophysics team lead. “Studying Ultima Thule is helping us understand how planets form — both those in our own solar system and those orbiting other stars in our galaxy.”
“The first exploration of a small Kuiper Belt object and the most distant exploration of any world in history is now history, but almost all of the data analysis lies in the future,” said Alan Stern of the Southwest Research Institute in Boulder, Colorado.
Data transmission from New Horizons will pause for about a week while the spacecraft passes behind the sun as seen from here on Earth. Data transmission resumes Jan. 10, and will then proceed to download the rest of the science data over the next 20 months.
“Those of us on the science team can’t wait to begin to start digging into that treasure trove,” said Stern. New Horizons completed the farthest flyby in history when it came within about 3,500 kilometers of Ultima Thule at 12:33 a.m. EST on Jan. 1, zooming past the object at more than 1,000 kilometers per hour.
“In the coming months, New Horizons will transmit dozens of data sets to Earth, and we’ll write new chapters in the story of Ultima Thule — and the solar system,” said Helene Winters, New Horizons Project Manager.
“New Horizons holds a dear place in our hearts as an intrepid and persistent little explorer, as well as a great photographer,” said Johns Hopkins Applied Physics Laboratory Director Ralph Semmel. “This flyby marks a first for all of us — APL, NASA, the nation and the world — and it is a great credit to the bold team of scientists and engineers who brought us to this point.”
“Reaching Ultima Thule from 4 billion miles away is an incredible achievement. This is exploration at its finest,” said Adam L. Hamilton, president and CEO of the Southwest Research Institute in San Antonio. “Kudos to the science team and mission partners for starting the textbooks on Pluto and the Kuiper Belt. We’re looking forward to seeing the next chapter.”
The mission team are already hoping to find the craft a new target based on how much fuel it still has, so watch this space!
ORIRIS-REX REACHES BENNU
Almost simultaneously with New Horizon’s Ultima Thule flyby, the OSIRIS-REx craft also broke records as it entered into the smallest ever orbit around the asteroid Bennu 110 million kilometers away from Earth.
“The team continued our long string of successes by executing the orbit-insertion maneuver perfectly,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “With the navigation campaign coming to an end, we are looking forward to the scientific mapping and sample site selection phase of the mission. Entering orbit around Bennu is an amazing accomplishment that our team has been planning for years,”
OSIRIS-REx’s first orbit marks a new leap for humankind. Never before has a spacecraft from Earth circled so close to such a small space object, one with barely enough gravity to keep the craft in a stable orbit. The craft is also moving very slowly.
Now, the spacecraft will circle Bennu about 1.75 kilometers from its center, closer than any other spacecraft has so far come to its celestial object of study. The closest previous orbit of a planetary body was in May 2016, when the Rosetta spacecraft orbited about seven kilometers from the center of the comet 67P/Churyumov-Gerasimenko. This short distance distance is essential in order to maintain its orbit and the spacecraft locked to Bennu, which has a gravitational force only 5-millionths as strong as Earth’s. The spacecraft is scheduled to orbit Bennu through until mid-February at its stately pace.
“Now that the OSIRIS-REx spacecraft is closer to Bennu, physical details about the asteroid will leap into sharper focus, and the spacecraft’s tour of this rubble pile of primordial debris will become increasingly detailed and focused,” OSIRIS-REx team members said.
“Our orbit design is highly dependent on Bennu’s physical properties, such as its mass and gravity field, which we didn’t know before we arrived,” said OSIRIS-REx’s flight dynamics system manager Mike Moreau, who is based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Up until now, we had to account for a wide variety of possible scenarios in our computer simulations to make sure we could safely navigate the spacecraft so close to Bennu. As the team learned more about the asteroid, we incorporated new information to hone in on the final orbit design,” he said.
This orbital phase will help improve our detailed models for Bennu’s gravity field, thermal properties, orientation, and spin rate,” said Dr. Dan Wibben, OSIRIS-REx maneuver and trajectory design lead at KinetX Aerospace. “This, in turn, will allow us to refine our trajectory designs for the even more challenging flight activities we will perform in 2019.”
Video credit: NASA
“Even though OSIRIS-REx is in the most stable orbit possible, Bennu’s gravitational pull is so tenuous that keeping the spacecraft safe will require occasional adjustments, said Dan Wibben, OSIRIS-REx maneuver and trajectory design lead at KinetX Aerospace in Simi Valley, California. “The gravity of Bennu is so small, forces like solar radiation and thermal pressure from Bennu’s surface become much more relevant and can push the spacecraft around in its orbit much more than if it were orbiting around Earth or Mars, where gravity is by far the most dominant force.”
“It’s simple logic: always burn toward the Sun if something goes wrong,” said Coralie Adam, OSIRIS-REx lead optical navigation engineer at KinetX. “Engineers can navigate the spacecraft back into orbit if it drifts away”, Adam said, although this is thought to be unlikely. “The navigation and spacecraft operations teams are focused on the first orbital phase. Their primary goal is to transition away from star-based navigation, which allowed the team to locate the spacecraft based on pictures of the star formations around it taken by the cameras onboard. Navigators use methods like this since there is no GPS in deep space and we can’t see the spacecraft from Earth-based telescopes. From this point forward, though, the OSIRIS-REx team will rely on landmarks on Bennu’s surface to track OSIRIS-REx, a more precise technique that will ultimately guide them to a sample-collection site clear of boulders and large rocks. After conducting a global imaging and mapping campaign during our recent preliminary survey phase, the science team has created 3-D models of Bennu’s terrain that we’re going to begin using for navigation around the asteroid. Another critical objective of this orbital phase, is to get a better handle on Bennu’s mass and gravity, features that will influence the planning of the rest of the mission, notably the short touchdown on the surface for sample collection in 2020. In the case of Bennu, we can only measure these features by getting OSIRIS-REx very close to the surface to see how its trajectory bends from Bennu’s gravitational pull.”
“The Orbital A phase will help improve our detailed models for Bennu’s gravity field, thermal properties, orientation, and spin rate,” said Wibben. “This, in turn, will allow us to refine our trajectory designs for the even more challenging flight activities we will perform in 2019.”
Next year the craft is planned to briefly touch the surface of the asteroid in order to take a sample and bring it back to Earth in 2023.
CHINA LANDS ON THE DARK SIDE OF THE MOON
In a first of its kind mission, China lands in the South Pole Aitken Basin, a huge ancient crater system, in order to carry out assorted geological and biological research and experiments. The Chang’e-4 Lander’s images have to be bounced off a satellite due to the Moon being tidally locked to the Earth.
The Chang’e-4 probe is aiming to explore a region named as the Von Kármán crater, located within the much larger South Pole-Aitken (SPA) Basin which is thought to have been formed by a giant impact early in the Moon’s history. The aim of the lander is to discover more about the geological make-up and formation of our nearest celestial neighbour.
“This huge structure is over 2,500 kilometers in diameter and 13km deep, one of the largest impact craters in the Solar System and the largest, deepest and oldest basin on the Moon,” Said Andrew Coates, professor of physics at UCL’s Mullard Space Science Laboratory in Surrey.
The Basin is thought to have been so large as to have possibly brought mantle rocks up to the surface
Chang’e also carries assorted plants, including potatoes and a flowering plant in a mini biosphere. It also has a panoramic camera, a radar to probe beneath the lunar surface, an imaging spectrometer to identify minerals, an experiment to examine the interaction of the solar wind with the lunar surface. Being on the dark side of the Moon also has potential for radio astronomy without interference from the Earth, so this is also something that will be investigated.
So congratulations to all the mission teams, Happy New Year and see you again next time!