Our Observations for the DART Mission

Our Questions for the DART Mission Team and their Answers

Is it fun doing your job (in NASA)?

Elena Adams, Chief Engineer : DART is awesome 

Richard Moissl, Head of Planetary Defence at European Space Agency (ESA): I really enjoy being able to contribute, working with many many other people, to making our planet safer

Why did you start working for NASA?

Ed Reynolds, Project Manager DART Mission:  Because I liked space

Did you want to be something else before, if yes what?

Ed Reynolds, Project Manager DART Mission: No

Nancy Chabot, Science Coordination Lead DART Mission:  I wasn't sure what I wanted to do, but I loved Star Wars and liked the idea of discovering new things and the wonder of seeing worlds not seen before

What is your best discovery?

Nancy Chabot, Science Coordination Lead DART Mission:  I loved seeing the detail on the asteroid as the spacecraft approached it.

For how long have you worked for NASA?

Ed Reynolds, Project Manager DART Mission: over 30 years

Do you have a least favourite thing you do?

Elena Adams, Chief Engineer : yes, but it is not in DART.  DART is awesome 

Is there ever going to be another DART Mission?

Richard Moissl, Head of Planetary Defence at European Space Agency (ESA): ESA is sending the HERA Mission next year to learn more about Didymos and Dimorphos and the new orbits - and to checkout the hole the spacecraft made in Dimorphos

Nancy Chabot, Coordination Lead DART Mission: it would be good to do it again with a smaller asteroid target

Why did they choose that asteroid (Dimorphos)?

Colin Snodgrass, Professor at Edinburgh University, DART Mission Team member: the asteroid system was chosen because it has an orbit that it is no threat to Earth, but also because it is a pair of asteroids with one orbiting the other like an asteroid moon.  Because of this orbit,  the light from the two objects which telesscopes measure changes depending on whether the one is in front of the other.  Plotting the brightness on a lightcurve graph means we can calculate how long it takes the smaller object (Dimorphos) to orbit the bigger one (Didymos).  This then means that it is possible to measure any change - which is what would be expected after the spacecraft hit Dimorphos and slowed it down.  This proved to be true - the time for an orbit changed by 33 minutes.

How long did it take to create the spacecraft?

The design and build phase of the project started in August 2018 and the spacecraft launched in November 2021.

How long did it take to get into space?

Ed Reynolds, Project Manager DART Mission: 10 months from launch to impact

If you had hit in Earth's atmosphere how loud would the noise be? or would there be a noise at all?

Professor Simon Green, Open University, DART Mission Team: An interesting question – and I’m not entirely sure of the answer.

The relative impact speed of the DART spacecraft was around 14 000 mph, which is somewhat less than the speed of meteors hitting the Earth’s atmosphere (>25 000 mph). Typical meteors (shooting stars) are small dust grains with sizes of millimetres or centimetres, and are decelerated in the upper atmosphere (~100 km) with no effect discernable from the ground except the brief flash as they excite the gas molecules in the atmosphere.  Meteors with masses comparable to the DART spacecraft (~600 kg) are much rarer (but still happen many times a year) produce fireballs with trails lasting many seconds and reach much lower altitudes before disintegrating, often resulting in a fraction of their material reaching the ground as meteorites. This is sometimes accompanied by a sonic boom heard over a large area.

Spacecraft in low Earth orbit occasionally re-enter the atmosphere at speeds closer to DART’s impact speed after the end of their operational lifetime. They also produce observable fireballs as they disintegrate at altitudes of ~70 km, with some components reaching the ground. These are often predicted and observed optically, but I’m not aware of any noise being heard from these.

I think the answer to the question is that there may be some noise generated as the spacecraft is decelerated, but the level would depend critically on where in the atmosphere the deceleration to sub-sonic speeds occurred as to whether a sonic boom would be transmitted and audible on the ground.

That’s the best I can do…

On the programme what was the ratio of men to women?

Elena Adams, Chief Engineer :  50% of the lead engineers are women (so a ratio of 1:1)

Is it likely for an asteroid or anything to hit the earth?

Richard Moissl, Head of Planetary Defence at European Space Agency (ESA): small pieces of space debris hit the Earth all the time.  For the bigger objects in the solar system we know where they are and their orbit and none of them are currently on trck to hit the Earth.  We haven't found all the small objects yet though, and those could still do some large damage if they hit the Earth.  That is why it is important that new telescopes (in space and on the ground) are set up to scan the sky for objects which could be a threat.  Then follow up observations can determine their orbit and assess the risk.  This is a worldwide effort and not just the professional astronomers, but amateurs (and schools!) too.

Did you have any doubts about this mission?

Elena Adams, Chief Engineer : Yes, many times.  But we worked through those doubts and made it happen.  It is OK to doubt because it makes you come up with solutions.

How long did it take for the spacecraft to hit Dimporphos?

Ed Reynolds, Project Manager DART Mission:  It took 10 months to get to the asteroid.  

How big does an asteroid have to be to wipe out all living beings on earth?

Richard Moissl, Head of Planetary Defence at European Space Agency (ESA): Very big!  The asteroid which is thought to have caused the extinction of the dinosaurs was about 10km big, but did not kill all of life (we re here to prove that!).  If an asteroid big enough to kill all life was in our solar system it would be bright for us to see a long way away, and so we would have detected it already. 

How many pixels are on the camera you used? 

Colin Snodgrass, Professor at Edinburgh University, DART Mission Team member: The DRACO camera had 2,560 × 2,160 pixels so a total of 5.5 million pixels.

What is the environmental impact of the Mission?

Ed Reynolds, Project Manager DART Mission: No environmental impact

Were there any malfunctions or difficulties?

Ed Reynolds, Project Manager DART Mission: Yes.  The spacecraft included an experimental solar electric propulsion system called NEXT-C.  The xenon ion thrusters were turned on and tested for 2 hours during the cruise part of the flight.  We detected an unexpected interaction with the spacecraft.  This was something that hadn’t been seen in tests and so to be safe we decided not to use the thrusters unless we really had to (eg if we missed the asteroid and had to come back to it!).  Thankfully we hit the asteroid first time J

The data collected from the 2 hour test will help the design and testing of future ion thrusters.

How much did the asteroid change course?

Combined analysis team: Using data from telescopes on all seven continents, the team calculated a 33-minute change in Dimorphos' orbit. The team also found that DART's crash did not change Didymos' orbital period around the asteroid duo's center of mass, which is still 2.26 hours. 

What is the most surprising thing you've learnt from the Mission?

Nancy Chabot, Coordination Lead DART Mission: The after effects of the impact, the way the explosion was seen live and the long lasting debris tail.  We didn't really expect that, and we are still monitoring it.  (And we've loved the observations schools have been making of this too.)

Ed Reynolds, Project Manager DART Mission: How well a team could work together

How did you pinpoint Didymos?

Nancy Chabot, Coordination Lead DART Mission: Many observations were made from Earth before the spacecraft got close to make sure the orbit was known to pinpoint where it would be at the time of impact.  I was fascinated watching on the day as the cameras showed the asteroid getting bigger and bigger and we saw detail.  

It was amazing to be able to hit someting that small even though it was 11million km away.

Carolyn Ernst, a planetary scientist at The Johns Hopkins University Applied Physics Laboratory (APL): A month before impact, the DART probe began sending home pictures once every five hours, which were processed by a ground optical navigation team.  About four hours before impact, researchers handed over control to DART and allowed it to navigate itself using its autonomous SMART Nav system, which also processed images onboard to first identify Didymos and later Dimorphos. The mission team already knew that Dimorphos would be hidden from the spacecraft's view for much of this time, so they kept DART moving toward Didymos until it was able to detect Dimorphos, the smaller and dimmer of the two — which it did 73 minutes before slamming into it.

Which comet is the oldest?

Colin Snodgrass, Professor at Edinburgh University, DART Mission Team member: all comets are made of material left over from the formation of the solar system 4.6 billion years ago.  The first comet to be recognised as a body which orbits the sun and returns at regular intervals was Halley's Comet (named after the astronomer who worked out how long it took to orbit the sun and predicted when it would next appear in the sky). 

What happens if you get hiccups in space?

General discussion at conference led to conclusion that hiccups were possible because they are caused by a twitch in your diaphragm.  But on a related question, Chris Hadfield, Canadian Astronoaut: You can't burp in space  - because the air, food and liquids in your stomach are all floating together like chunky bubbles. If you burp, you throw up into your mouth. So guess where the trapped air goes?

What is the maximum people a rocket can fit?

Starship hopes to be able to take 100 people - but it needs lots more development and testing beofre that could happen.

How long would it take to make proper tech to get to Jupiter if it's even possible?

Helen Usher researcher at the Open University: The European Space Agency (ESA) has just launched a Mission called JUICE which will study the moons of Jupiter.  It will take 8 years to get to Jupiter.  ESA started project preparation in 2012.

Is it possible to walk on Saturn's ring or is the dust and rock too thin?

From a discussion with different people the conclusion is that you might be able to stand on some of the bigger boulders and hop between them in the non-gravity environment, but the rings themselves are not dense enough to walk on.

How much money would it cost to get one of the 2m telescopes?

Dill Faulkes, the founder of the Faulkes Telescope Project (in 1998), and who paid for their construction and then installation in Hawaii and Australia: Each of the two 2m telescopes cost me £4.45 million just for the hardware!  We then had to get them from Liverpool to the sites up to the mountains which was also very expensive!

What is the energy that keeps the Universe expanding?

That is an excellent question that is puzzling scientists!