The Space Missions of 2018

2018 has definitely been a big year for space, and space exploration. I have managed to capture a few of the great moments like the launch of InSight, JAXA landing rovers on an asteroid, and the launch of the Parker Probe. There have been a few others that are notable mentions, and that is the point of this post, to talk about some great launched missions, and others that have finished their jobs, purposely or forced.

Bepicolombo

The British built Bepicolombo launched in October 20th, to begin its 7 year journey to visit Mercury. Currently one of the least explored planets in the solar system, Bepicolombo intends to change that. When it arrives in late 2025 it will endure temperatures of over 350 °C, and be there for at least a year, possibly for twice that. It is made up of two spacecraft, the Mercury Planet Orbiter (MPO) lead by ESA, and the Mercury Magnetospheric Orbiter (MMO) lead by JAXA. The aim is to measure the composition, atmosphere and magnetosphere of Mercury to understand its history. This could lead to understanding more about how other planets such as Earth formed. BepiColombo is named after Professor Giuseppe (Bepi) Colombo (1920-1984) from the University of Padua, Italy. He made big leaps in understanding Mercury, and suggested to NASA how to use a gravity-assist swing-by of Venus to place Mariner 10 into a solar orbit of Mercury.

Bepicolombo artists impression
Artist’s impression of the BepiColombo spacecraft in cruise configuration. The Mercury Transfer Module is at the bottom. The Mercury Planetary Orbiter is in the middle. The Mercury Magnetospheric Orbiter sits inside the sunshield, visible at the top. Credit: ESA/ATG medialab

InSight

Back in May I posted about how an Atlas V had just lifted the Mars Insight lander. In late November the $814 million lander it reached its target of the Elysium Planitia region of Mars, landing safely. The aim is for it investigate how the processes that shaped all the inner rocky planets more than 4 billion years ago worked. It uses two seismometers (one of which built by RAL space in the UK) and a number of other instruments to study the crust, mantle and core of the red planet. It works by measuring how much the area shakes when asteroids hit the planet. Also measuring the heat flow and precision tracking it is getting a glimpse of Mars we have yet to see. The launch also allowed for two cubesats, MarCO-A and MarCO-B to be the first to be launched into deep space. The first test of miniaturised cubesat technology being used on another planet. This mission will be one to watch for the near future.

There’s a quiet beauty here. Looking forward to exploring my new home. #MarsLanding pic.twitter.com/mfClzsfJJr— NASA InSight (@NASAInSight) November 27, 2018

Kepler

A bit sadder news is the end of the Kepler space telescope after 9 years service. It has collected a huge amount of data in its lifetime, finding the night sky is filled with billions of hidden planets, more planets than stars. This may seem obvious but is not easy to prove. During its time the planet hunter has found evidence of more than 2,600 planets outside our solar system, and left hints at many more, paving the way for future planet hunters and getting good engineering data on what works and what doesn’t. Telescopes such as ARIEL which will launch in the net decade will have better design due to Kepler. The space telescope had been running low on fuel for months, and struggled to point the correct way. After the 4 year mission it continued to work a different mission named K2. In October it was officially declared dead, left in orbit as it may have been dangerous for it to enter the atmosphere.

The Kepler Space Telescope mission, by the numbers
The Kepler Space Telescope mission, by the numbers. Credit: NASA/Ames/Wendy Stenzel

Parker Solar Probe

Back in august I wrote about the classic Delta IV heavy launching with the Parker Solar Probe aboard. The aim is to get closer to the sun than previously possible. Over the next seven years the probe will make 24 close approaches to the sun, with the aim of eventually getting within 3.8 million miles of the surface. The previous record (that Parker has now broken) was 26.6 million miles, set in 1976. It will revolutionise our understanding of the sun, and how the changing conditions can affect the solar system. It will use Venus’ gravity to slowly get closer to the sun. As a reference, we are 93 million miles away from the sun. It will eventually fly through the sun’s outer atmosphere, known as the Corona for the first time, getting brand new, in situ measurements. The spacecraft has a 4.5 inch thick carbon composite shield to protect it from the heat and radiation. The temperatures will reach over 1300 C.

Parker Solar Probe in the Fairing
Parker Solar Probe in the Fairing, ready to be put on the rocket in the clean room. Credit: NASA/Johns Hopkins APL/Ed Whitman

TESS

Back in April I posted about the launch of the TESS exoplanet hunter by a Falcon 9. I have already talked about exoplanets and planet hunters, and this is a big part of that plan. TESS stands for Transiting Exoplanet Surveying Satellite, and it does what it says on the tin, it is surveying the sky for potential exoplanets. Basically it is looking for exoplanets that could harbour life. The expectation is that it will catalog thousands of planet candidates and vastly increase the known number of exoplanets. Approximately 300 are expected to be Earth-sized and super-Earth-sized exoplanets that can then use the future more complex telescopes such as JWST to look at in more detail. The satellite will look at the sky for two years by breaking it up into 26 sections, and looking at each one for 27 days at a time. Unlike Kepler and K2 TESS will be looking at brighter stars, meaning ground based observatories can corroborate the observations.

the TESS telescope
The TESS satellite before launch, the four cameras can be seen on the top of the spacecraft; Credit: NASA.

Dawn

In September I posted about the Dawn spacecraft and the rise of Ion Engines. With the loss of the Dawn mission around the same time as Kepler, they ran out of fuel within two days of each other. The 11 year Dawn mission racked up a few very important records. It is the first spacecraft to orbit two different celestial bodies, and the first to orbit any object in the main asteroid belt between Mars and Jupiter. It is also a record breaker for electric speed. Travelling over 25,700 mph. Visiting Ceres and Vesta, it found out some very important scientific data that tells us a huge amount about the formation of our solar system. With a large proportion of the meteorites hitting Earth coming from these two bodies, Dawn showed the difference between the potential dwarf planets. One of the early uses of ion engines, it also showed the potential of the efficient form of travel, and now many more satellites are using them.

Dawn prior to encapsulation at its launch pad on July 1, 2007. Credit: NASA/Amanda Diller

Mars Rovers

This is a mixed bag, we have already had great news about the InSight lander, with it recording sounds of Martian winds, the rovers also have big news this year. In June the Curiosity rover found Organic matter in the Martian soil. The samples, taken from 3 billion year old mudstone contained complex hydrocarbons. This along with its detection of methane changes in the atmosphere are one step along the way to finding evidence of life on other planets. There have also been many more photos from the red planet, with Curiosity taking a few more selfies. See here how the car sized rover achieves the great pictures. On the other side of it there was a huge Martian storm that may have killed the Opportunity rover by covering the solar panels in dust. Although there are still hopes the rover can start communications again, we will have to see.

Curiosity in a dust storm
An image shared by Seán Doran on Sunday of the Mars Curiosity in the middle of a dust storm reported to cover an area the size of the US and Russia Combined. CredIt: NASA/JPL/Seán Doran.

Asteroid Rovers

In late september, another great story came out, that JAXA (the Japanese space agency) successfully landed a number of rovers on an asteroid. Still to launch all of the four onto the surface, there are already great images from the surface of an asteroid. The little rovers use a hopping mechanism to get around, as the gravity on the asteroid is so small a wheeled rover just wouldn’t work. The spacecraft will also be attempting to collect samples to return to Earth in the coming years. The Hayabusa 2 probe is a follow up to the Hayabusa probe which was not a sample return. The second launched on December 3rd 2014 and rendezvoused with the near-earth asteroid 162173 Ryugu on the 27th of June 2018. Currently in the process of surveying the asteroid for a year and a half, it will depart in December 2019, returning to Earth in December 2020.

 MINERVA-II image
First pictures from a MINERVA-II-1 rover that landed on the asteroid. Credit: JAXA.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts this year! So all have a Happy New Year, and here’s to a great 2019 in space!

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The Dawn of Ion Engines

Ion thrusters are becoming a bigger and bigger part of modern satellite design. Over 100 geosynchronous Earth Orbit communication satellites are being kept in the desired locations in orbit using this revolutionary technology. This post is about its most amazing achievement to date, the Dawn Spacecraft. Just reported that it is at the end of its second extension of the mission it has a few records under its belt. It is the first spacecraft to orbit two different celestial bodies, and the first to orbit any object in the main asteroid belt between Mars and Jupiter. It is also a record breaker for electric speed. Travelling over 25,700 mph it is 2.7x faster than the previous fastest electric thrusted spacecraft. That is a comparable speed to the Delta 2 launch vehicle that got it to space in the first place.

Delta 2 launch
The Dawn spacecraft launching on a Delta 2 rocket from Cape Canaveral Air Force Station SLC 17 on Sept 27th, 2007. Credit: NASA/Tony Gray & Robert Murra

The Dawn mission was designed to study two large bodies in the main asteroid belt. This is to get a deeper insight into the formation of the solar system . It also has the added benefit of testing the ion drive in deep space for much longer than previous spacecraft. Ceres and Vesta are the two most massive bodies in the belt, and are also very useful protoplanets from a scientific standpoint. Ceres is an icy and cold dwarf planet whereas Vesta is a rocky and dry asteroid. Understanding these bodies can bridge the understanding of how the rocky planets and icy bodies of the solar system form. It could also show how some of the rocky planets can hold water/ice. In 2006 the International Astronomical Union (IAU) changed the definition of what a planet is, and introduced the term “dwarf planet”. This is the change that downgraded Pluto from its planet status, although that has been argued to be wrong by Dr. Phil Metzger in a recent paper. Ceres is classified as a dwarf planet. As Dawn arrived at Ceres a few months before New Horizons reached Pluto, Dawn was the first to study a dwarf planet.

Dawn prior to encapsulation at its launch pad on July 1, 2007. Credit: NASA/Amanda Diller

The ion engine is so efficient that without them a trip to just Vesta would need 10 times more propellant, a much larger spacecraft, and therefore a much larger launch vehicle (making it much more expensive). The ion propulsion system that it uses was first proven by Deep Space Mission 1, along with 11 other technologies. Dawn has three 30 cm diameter (12 inch) ion thrust units. They can move in two axis to allow for migration of the center of mass as the mission progresses. The attitude control system can also use the movable ion thrusters to control the attitude. The mission only needs two of the thrusters to complete the mission, the third being a spare. All three have been used at some point during the mission, one at a time. As of September 7th 2018 the spacecraft has spent 5.9 years with the ion thrusters on, which is about 54% of its total time in space. The thrust to its first orbit took 979 days, with the entire mission being over 2000 days. Deep Space 1’s mission in contrast lasted 678 days before the fuel ran out.

An artist’s impression of Dawn with its ion thrusters on. Credit: NASA

The thrusters work by using electrical charge to accelerate ions from xenon fuel to speeds 7-10 times that of chemical engines. The power level and the fuel feed can be adjusted to act like a throttle. The thruster is very thrifty with its fuel, using a minor 3.25 milligrams of xenon per second, roughly 280g per day, at maximum thrust. The spacecraft carried 425 kg (937 pounds) of xenon propellant at launch. Xenon is a great fuel source because it is chemically inert, easily stored in compact form. Plus the atoms are very heavy so they provide large thrust compared to other comparable candidate propellants. At launch on Earth the xenon was 1.5 times the density of water. At full thrust the ion engines produce a thrust of 91 mN, which is roughly the force needed to hold a small sheet of paper. Over time these minute forces add up and over the course of years can produce very large speeds. The electrical power is produced by two 8.3 m (27 ft) x 2.3 m (7.7 ft) solar arrays. Each 18 meter squared (25 yard squared) array is covered in 5,740 individual photo voltaic cells. They can convert 28% of the sun’s energy into useful electricity. If these panels were on Earth they would produce 10 kW of energy. Each of the panels are on gimbals that mean they can turn any time to face the sun. The spacecraft uses a nickel-hydrogen battery to charge up and power during dark points in the mission.

The dawn mission patch.  This logo represents the mission of the Dawn spacecraft. During its nearly decade-long mission, Dawn will study the asteroid Vesta and dwarf planet Ceres Credit: NASA.

Vesta was discovered on March 29th 1807 by astronomer Heinrich Wilhelm Olbers, and is named after the Roman virgin goddess of home and hearth. The Dawn mission uncovered many unique surface features of the protoplanet ,twice the area of California, that have intrigued scientists. Two colossal impact craters were found in the southern hemisphere, the 500 km (310 miles) wide Rheasilvia basin, and the older 400 km (250 miles) wide Veneneia crater. The combined view of these craters was apparent even to the Hubble telescope. Dawn showed that the Rheasilvia crater’s width is 95% of the width of Vesta (it’s not perfectly spherical) and is roughly 19 km (12 miles) deep. The central peak of the crater rises to 19-25 km (12-16 miles) high, and being more that 160 km (100 miles) wide, it competes with Mars’ Olympus Mons as the largest mountain in the solar system. The debris that was propelled away from Vesta during the impacts made up 1% of its mass, and is now beginning its journey through the solar system. These are known as Vestoids, ranging from sand and gravel all the way up to boulders and smaller asteroids. About 6% of all meteorites that land on Earth are a result of this impact.


The brave new world of 4 Vesta, courtesy of NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

Dawn mapped Vesta’s geology, composition, cratering record and more during its orbit. It also managed to determine the inner structure by measuring its gravitational field. The measurements were consistent with the presence of an iron core of around 225 km (140 miles), in agreement with the size predicted by
howardite-eucrite-diogenite (HED)-based differentiation models. The Dawn mission confirmed that Vesta is the parent body of the HED meteorites, by matching them with lab based measurements. These experiments measured the elemental composition of Vesta’s surface and its specific mineralogy. These results confirm that Vesta experienced pervasive, maybe even global melting, implying that differentiation may be a common history for large planetesimals that condensed before short-lived heat-producing radioactive elements decayed away. The pitted terrains and gullies were found in several young craters. This could be interpreted as evidence of volatile releases and transient water flow. Vesta’s composition is volatile-depleted, so these hydrated materials are likely exogenic (formed on the surface).

A colour coded topographic map from the Dawn mission of the giant asteroid Vesta. Credit: NASA/JPL

The first object ever discovered in the main asteroid belt was Ceres. Named after the Roman goddess of corn and harvest, it was discovered by Italian astronomer Father Giuseppe Piazzi in 1801. Initially classified as a planet, it was later classified as an asteroid as more objects were found in the same region. In recognition of its planet like properties (being very spherical) it was designated a dwarf planet in 2006 along with Pluto and Eris. Observed by the Hubble telescope between 2003 and 2004, it was shown to be nearly spherical, and approximately 940 km (585 miles) wide. Ceres makes up 35% of the mass of the main asteroid belt. Before Dawn there were plenty of signs of water on Ceres. First, its low density indicates that it is 25% ice by mass, which makes it the most water rich body in the inner solar system after Earth (in absolute amount of water). Also, using Hershel in 2012 and 2013, evidence of water vapor, probably produced by ice near the surface transforming from solid to gas (known as sublimating).

Dwarf planet Ceres is shown in these false-color renderings, which highlight differences in surface materials. Credit: NASA/JPL-CalTech/UCLA/MPS/DLR/IDA

Acquiring all the data it needed by the middle of 2016, Dawn measured its global shape, mean density, surface morphology, mineralogy, elemental composition, regional gravity and topography at exceeded resolutions. The imaging from the mission showed a heavily cratered surface with bright features. Often referred to as “bright spots” they are deposits of carbonates and other salts. Multiple measurements showed an abundance of ice at higher latitudes. However the retention of craters up to 275 km (170 miles) in diameter argue for a strong crust, with lots of hydrated salts, rocks and clathrates (molecules trapped in a cage of water molecules). Gravity and topography data also indicated that that Ceres’ internal density increases with depth. This is evidence for internal differentiation resulting from the separation of the dense rock from the low density water-rich phases in Ceres history. The rock settled to form an inner mantle overlain with a water-rich crust. This internal differentiation is typical of small planets like Ceres and Vesta that Sets them apart from asteroids.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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