12.05.2024
Exploring asteroid Apophis using miniature satellites
The scenario could be lifted straight from a disaster novel: On Friday, April 13, 2029-a date that alone might evoke unease-the asteroid known as (99942) Apophis will make a remarkably close approach to Earth, missing us by just 30,000 kilometers. Visible as a mere speck of light in the night sky from places like Wurzburg, this proximity provides a unique observational opportunity.
Apophis, measuring about 340 meters in diameter, poses a significant risk. Should it collide with Earth, the impact could create a crater several kilometers wide, potentially devastating a region as large as Central Europe, according to Jonathan Mannel, a research associate at the Julius-Maximilians-Universitat Wurzburg's (JMU) Space Technology Chair.
However, there is no immediate threat as NASA's calculations confirm Apophis will avoid Earth for at least the next century. Identified in 2004 as a potentially hazardous object, Apophis has been closely monitored by space agencies worldwide.
Research Opportunity Brought by Apophis
Asteroids are irregularly shaped celestial objects orbiting the sun. Approximately 1.3 million asteroids have been identified, with about 2,500 classified as potentially hazardous. This designation is given to near-Earth asteroids positioned within 20 lunar distances from Earth and larger than 140 meters.
The trajectory, structure, and potential interactions of asteroids when they pass near other celestial bodies raise several scientific questions. Apophis presents a rare research opportunity due to its size and the infrequency of such close encounters with Earth-events that happen once every 1,000 years. This situation offers a practical moment to potentially develop defensive strategies against asteroid threats.
Investigating Mission Concepts in Germany
Professor Hakan Kayal's team at JMU is exploring how Germany could contribute to studying Apophis through the NEAlight project, supported with approximately 300,000 euros from the Federal Ministry for Economic Affairs and Climate Action. Under project leader Jonathan Mannel, and with research assistants Tobias Neumann and Clemens Riegler, the team is assessing three small satellite mission concepts derived from the 2023 SATEX project, which evaluated the capabilities of small satellites for interplanetary tasks.
The first concept involves a national mission where a small satellite would trail Apophis as it approaches Earth, documenting any changes through photographs and measurements. This mission faces numerous technical challenges due to the distance and autonomy required.
The second concept involves collaboration on the European RAMSES mission, which would employ a larger satellite equipped with smaller satellites, telescopes, and other instruments to monitor Apophis. Here, a satellite from Wurzburg would participate, potentially enhancing the scientific yield and reducing the technical demands on JMU's team.
The third concept proposes a brief encounter where a JMU-built satellite would pass close to Apophis to capture photographs. This mission would require minimal resources but offer limited observation time and potentially less scientific data.
Further Plans and Project Goals
By April 2025, Kayal's team aims to finalize the requirements for these scenarios, outline the mission architectures, and assess the feasibility of each approach. This effort will also inform future projects involving interplanetary small satellites aimed at other near-Earth objects or lunar missions.
Launched in early May 2024, the NEAlight project is set to conclude after a year, taking place at the Interdisciplinary Research Centre for Extraterrestrial Studies (IFEX) at JMU's Chair for Space Technology. Funding for the project comes from the German Aerospace Centre (DLR) with an allocation of approximately 306,000 euros provided by the Federal Ministry of Economics and Climate Action.
Quelle: SD
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Update: 18.07.2024
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Asteroid Apophis will visit Earth in 2029, and this European satellite will be along for the ride
By characterizing Apophis and how it reacts to being in Earth's gravitational field, Ramses will boost our knowledge of NEOs and planetary defense.
An animation shows Apophis' 2029 path compared to the swarm of satellites orbiting Earth. (Image credit: NASA/JPL-Caltech)
The European Space Agency is fast-tracking a new mission called Ramses, which will fly to near-Earth asteroid 99942 Apophis and join the space rock in 2029 when it comes very close to our planet — closer even than the region where geosynchronous satellites sit.
Ramses is short for Rapid Apophis Mission for Space Safety and, as its name suggests, is the next phase in humanity's efforts to learn more about near-Earth asteroids (NEOs) and how we might deflect them should one ever be discovered on a collision course with planet Earth.
In order to launch in time to rendezvous with Apophis in February 2029, scientists at the European Space Agency have been given permission to start planning Ramses even before the multinational space agency officially adopts the mission. The sanctioning and appropriation of funding for the Ramses mission will hopefully take place at ESA's Ministerial Council meeting (involving representatives from each of ESA's member states) in November of 2025. To arrive at Apophis in February 2029, launch would have to take place in April 2028, the agency says.
This is a big deal because large asteroids don't come this close to Earth very often. It is thus scientifically precious that, on April 13, 2029, Apophis will pass within 19,794 miles (31,860 kilometers) of Earth. For comparison, geosynchronous orbit is 22,236 miles (35,786 km) above Earth's surface. Such close fly-bys by asteroids hundreds of meters across (Apophis is about 1,230 feet, or 375 meters, across) only occur on average once every 5,000 to 10,000 years. Miss this one, and we've got a long time to wait for the next.
When Apophis was discovered in 2004, it was for a short time the most dangerous asteroid known, being classified as having the potential to impact with Earth possibly in 2029, 2036, or 2068. Should an asteroid of its size strike Earth, it could gouge out a crater several kilometers across and devastate a country with shock waves, flash heating and earth tremors. If it crashed down in the ocean, it could send a towering tsunami to devastate coastlines in multiple countries.
Over time, as our knowledge of Apophis' orbit became more refined, however, the risk of impact greatly went down. Radar observations of the asteroid in March of 2021 reduced the uncertainty in Apophis' orbit from hundreds of kilometers to just a few kilometers, finally removing any lingering worries about an impact — at least for the next 100 years. (Beyond 100 years, asteroid orbits can become too unpredictable to plot with any accuracy, but there's currently no suggestion that an impact will occur after 100 years.) So, Earth is expected to be perfectly safe in 2029 when Apophis comes through. Still, scientists want to see how Apophis responds by coming so close to Earth and entering our planet's gravitational field.
"There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface," said Patrick Michel, who is the Director of Research at CNRS at Observatoire de la Côte d’Azur in Nice, France, in a statement. "Nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface."
By arriving at Apophis before the asteroid's close encounter with Earth, and sticking with it throughout the flyby and beyond, Ramses will be in prime position to conduct before-and-after surveys to see how Apophis reacts to Earth. By looking for disturbances Earth's gravitational tidal forces trigger on the asteroid's surface, Ramses will be able to learn about Apophis' internal structure, density, porosity and composition, all of which are characteristics that we would need to first understand before considering how best to deflect a similar asteroid were one ever found to be on a collision course with our world.
Besides assisting in protecting Earth, learning about Apophis will give scientists further insights into how similar asteroids formed in the early solar system, and, in the process, how planets (including Earth) formed out of the same material.
One way we already know Earth will affect Apophis is by changing its orbit. Currently, Apophis is categorized as an Aten-type asteroid, which is what we call the class of near-Earth objects that have a shorter orbit around the sun than Earth does. Apophis currently gets as far as 0.92 astronomical units (137.6 million km, or 85.5 million miles) from the sun. However, our planet will give Apophis a gravitational nudge that will enlarge its orbit to 1.1 astronomical units (164.6 million km, or 102 million miles), such that its orbital period becomes longer than Earth's.
It will then be classed as an Apollo-type asteroid.
Ramses won't be alone in tracking Apophis. NASA has repurposed their OSIRIS-REx mission, which returned a sample from another near-Earth asteroid, 101955 Bennu, in 2023. However, the spacecraft, renamed OSIRIS-APEX (Apophis Explorer), won't arrive at the asteroid until April 23, 2029, ten days after the close encounter with Earth. OSIRIS-APEX will initially perform a flyby of Apophis at a distance of about 2,500 miles (4,000 km) from the object, then return in June that year to settle into orbit around Apophis for an 18-month mission.
Furthermore, the European Space Agency still plans on launching its Hera spacecraft in October 2024 to follow-up on the DART mission to the double asteroid Didymos and Dimorphos. DART impacted the latter in a test of kinetic impactor capabilities for potentially changing a hazardous asteroid's orbit around our planet. Hera will survey the binary asteroid system and observe the crater made by DART's sacrifice to gain a better understanding of Dimorphos' structure and composition post-impact, so that we can place the results in context.
The more near-Earth asteroids like Dimorphos and Apophis that we study, the greater that context becomes. Perhaps, one day, the understanding that we have gained from these missions will indeed save our planet.
Quelle: SD