Tuesday, April 23, 2019

[Spaceflight] New Horizons - After Ultima Thule

Since 2015 I've been following with excitement the astonishing discoveries of space probe New Horizons. Launched in 2006 with the primary mission goal to perform a Pluto flyby, the small probe is the fastest man-made object ever sent into space.
New Horizons
New Horizons, Credit: NASA
On its journey to the outer edge of the solar system, it first passed by the asteroid belt in 2006 and took images of the small asteroid 132524 APL. In 2007 it performed a Jupiter flyby and collected valuable data about the gas giant's atmosphere, magnetosphere, ring system and moons. The flyby also provided the probe with a gravity assist and accelerated its flight time to Pluto by three years.

In July 2015 the probe finally reached its destination and the mission scientists were able to successfully orchestrate the first Pluto flyby ever. The probe returned high resolution images of Pluto and its moons and highly valuable data about the dwarf planet, making the mission a much celebrated success. But Pluto proved to be by far not the last discovery of New Horizons.
Picture of Pluto by New Horizons, Credit: NASA
The Kuiper belt and Ultima Thule

After its brief encounter with Pluto, New Horizons proceeded on its path towards interstellar space, soon getting into range of the Kuiper belt. The Kuiper belt is an asteroid belt that consists of more than 70000 sub-planetary objects, orbiting at a distance of 30-50 AU from the sun. Since their orbit lies far beyond Neptune, they belong to the group of trans-Neptunian objects (TNOs). Prominent Kuiper belt objects are besides Pluto the dwarf planets Eris, Haumea and Makemake. Due to their great distance from Earth we practically knew nothing about those dark and cold worlds.

Luckily the New Horizons team could secure a mission extention to study the Kuiper belt and perform a flyby of Kuiper belt object Ultima Thule/2014 MU69, which was again a full success. On New Year's Day 2019 the spacecraft passed by Ultima Thule in a distance of 3500 km, marking the most distant flyby in the history of spaceflight. Ultima Thule turned out to be a contact binary and provided us with valuable data about the Kuiper belt objects.
Ultima Thule, Credit: NASA
Further exploration of the Kuiper belt

But what is the future of New Horizons? During the next two years the probe will be busy transmitting the data from the Ultima Thule flyby. In the meantime it will gather information about the gas, dust and plasma composition of the Kuiper belt and the composition of the solar wind in the outer solar system.
New Horizons trajectory before and after Ultima Thule, Credit: NASA
With its telescope LORRI (Long Range Reconnaissance Imager) it is also able to investigate Kuiper belt objects (KBOs) which are not observable from Earth. The New Horizons probe offers a unique opportunity to study those distant objects and search for satellite systems around them. Further observations might be possible if the mission scientists find a way to replace the now expendable flyby software with software that allows faster data transmission.

In January 2019 the probe already observed the Kuiper belt object 2014 OS393, which was originally an alternate flyby target for Ultima Thule. New Horizons passed by the small asteroid in a distance of 0.1 AU (15 million km). In March 2019 the Kuiper belt object 2014 PN70, also an original flyby candidate, followed with similar distance. The images should reveal more about the shape, surface properties, rotation period and satellite system of the objects. The gathered data will help putting the Ultima Thule data into context and extracting general information about the properties of Kuiper belt objects.
Possibility of extended missions after 2021

The mission around Ultima Thule will end in 2021, though it is highly probable the New Horizons mission will get extended again. The spacecraft has enough fuel and power to remain functionable until the 2030s. The mission leader Alan Stern believes in a third flyby in the 2020s if a suitable Kuiper belt object (KBO) can be found. The search for dimmer KBOs in the spacecraft's trajectory is ongoing with the Hubble telescope and New Horizon's own telescopes. The launch of the Large Synoptic Survey Telescope in Chile in 2022 is also promising new discoveries in the outer reaches of the solar system.

It is estimated the RTG (radioisotopic thermoelectric generator) will last until 2035. In 2038 New Horizons will reach a distance of 100 AU (Astronimical Units). Should it still be functionable it will explore the outer edges of the heliosphere and eventually follow the Voyager probes into interstellar space.
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