NASA’s Small Bodies Assessment Group is encouraging NASA to find a way to send a spacecraft to study the asteroid Apophis before it reaches Earth in 2029. Apophis will come close enough for ground-based telescopes to get a good look as it whizzes by, but scientists want before and after measurements, too. Plans are already set for detailed in-space studies afterwards, but not before. One option is repurposing a pair of small spacecraft called Janus about to be put in storage even though they are built and ready to launch.
SBAG just posted the findings from its July 2023 meeting, one of which “encourages NASA to pursue a mission opportunity, achievable within available resources, to explore Apophis prior to its close Earth approach, whether initiating its own effort or via collaboration with foreign and domestic partners.”
Scientists have calculated and recalculated Apophis’s orbit and are confident it will not collide with Earth, but it will come within about 20,000 miles (32,000 kilometers) on Friday, April 13, 2029 and be visible to the naked eye. That distance from Earth’s surface is about the same as geosynchronous orbit where a large number of satellites are located. JPL put together this animation of Apophis sailing through that region.
Apophis is not nearly as big as the 6-mile (10-kilometer) wide asteroid that hit Earth 65 million years ago and led to the extinction of the dinosaurs, but it is much larger than the meteor that exploded over Chelyabinsk, Russia in 2013. The Chelyabinsk meteor was about 65 feet (20 meters) in diameter; Apophis is 1,100 feet (340 meters).
Although Apophis won’t hit Earth, it is likely to attract a lot of public interest. A recent Pew Research Center poll found that 60 percent of respondents think monitoring asteroids or other objects that could impact Earth should be NASA’s top priority. In its most recent Decadal Survey for planetary science, the National Academies of Sciences, Engineering, and Medicine also highlighted planetary defense as a key area for investment.
Scientists want to study Apophis before and after its close approach to Earth to determine how it changes. So far NASA is only committed to collecting data afterwards using the OSIRIS-REx spacecraft once it drops off a canister full of samples from the asteroid Bennu next month. Renamed OSIRIS-APophis EXplorer (OSIRIS-APEX), the main spacecraft will continue its journey around the Sun and meet up with Apophis shortly after it passes Earth and spend 18 months conducting detailed studies.
The question is how to get data before the encounter. At the 8th Planetary Defense Conference in April, Bhavya Lal, then NASA’s Associate Administrator for Technology, Policy and Strategy, urged the international community to send a “small fleet” of reconnaissance spacecraft to Apophis in advance of the encounter with Earth.
Budget constraints are a challenge, however.
One option is to use the two small (50 kilogram) Janus spacecraft that were designed and built to share a ride with NASA’s Psyche mission and independently fly past binary asteroids along the same path. Psyche was supposed to launch in 2022, but last minute problems delayed it until this October. That changed the trajectory the spacecraft will take to its destination, the asteroid Psyche in the main asteroid belt between Mars and Jupiter, and there no longer are any viable targets for Janus.
The two spacecraft are already built and ready for launch. Part of NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx) program to demonstrate how small satellites can be used for planetary exploration, the two came in slightly under the $55 million cap at $49 million.
At the SBAG meeting, Principal Investigator (PI) Daniel Scheeres from the University of Colorado Boulder, said his team developed a proposal to use the Janus spacecraft to study Apophis. Although NASA’s Planetary Science Division (PSD) requested the study, in the end PSD concluded there wasn’t sufficient money. On June 28, 2023, they directed that the Lockheed Martin-built spacecraft be put in storage.
Scheeres said once the spacecraft are in storage it would take about a year to get them ready again for spaceflight, emphasizing that’s a conservative estimate.
SBAG did not go as far as to say Janus should be used for Apophis, but in a separate finding urged NASA “to define an appropriate path forward for spacecraft that are delivered to storage without a launch date” like Janus.
“There is currently a clear pathway for the end of active missions, however, the fate of shelved missions remains uncertain. Some missions in NASA’s PSD portfolio are economical, efficient, and innovative but due to lack of launch opportunities, budgetary pressures, etc., these missions are at higher risk of being delayed or shelved. SBAG suggests that NASA recognize the resources and efforts that have already been spent on the development of the shelved missions (e.g., Janus) and encourages NASA to define a process to be used when putting flight hardware into storage that will establish the criteria for exiting storage. Following a process with clearly documented criteria will increase transparency and enable the community to help find alternative paths forward, including as international or private collaborations or redirecting the missions to other suitable targets.” Finding #1 from SBAG 29, July 11-13, 2023
SBAG is part of NASA’s external advisory process to get input from the scientific community. Assessment groups like SBAG feed their findings forward to NASA’s formal advisory committees. SBAG’s members study small bodies in the Solar System like asteroids and comets and work with NASA’s Planetary Science Advisory Committee that advises PSD, part of the Science Mission Directorate.
PSD’s budget is under considerable stress. Although the total amount is higher than ever before, the PSD portfolio includes extremely expensive missions like Europa Clipper and Mars Sample Return, each costing more than $5 billion. In order to cover the cost of Psyche’s one-year delay, NASA postponed a completely unrelated mission to Venus, VERITAS, for at least three years. PSD also had to redirect money to fund the NEO Surveyor mission, a space-based telescope to locate asteroids. NASA planned to indefinitely defer NEO Surveyor, but Congress insisted it launch no later than 2028. NASA’s search for asteroids is in response to congressional direction in George E. Brown, Jr. Near-Earth Object Survey Act, part of the 2005 NASA Authorization Act.
In short, finding money to send a spacecraft to collect data on Apophis before it reaches Earth would be difficult, but at least the Janus spacecraft provide an option that defrays some of the cost since they are already built.
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