Hayabusa2 is safe and sound after successfully using its explosive-packed SCI experiment to create an artificial crater on Ryugu. JAXA released images from DCAM3, the small camera Hayabusa2 left behind to monitor the explosion and crater formation, that show a cloud of debris spraying into space.
The spacecraft successfully retreated behind Ryugu during the explosion, and is now making a two-week journey that will carry it more than 100 kilometers away from Ryugu while any debris from the crater formation settles or floats into interplanetary space.
Hayabusa2 left its 20-kilometer home position at 04:00 UTC on 4 April, descending towards Ryugu at 40 centimeters per second. At about 5 kilometers from the surface, it slowed to just 10 centimeters per second, and JAXA flight controllers granted it final clearance to proceed. Its target region for SCI came into view at about 19:35 UTC:
[SCI] First image is the navigation image received on April 5, 04:35 JST. The target area of the SCI is visible and this is enlarged & accentuated in the second image on the left, with previously taken data on the right. We are aiming for this area. pic.twitter.com/uSvd987vhv— [email protected] (@haya2e_jaxa) April 4, 2019
JAXA continued to receive real time images from the spacecraft up until Hayabusa2 armed its SCI package and transitioned into fully autonomous mode. The final image, received 5 April at 01:21 UTC, was not completely downlinked from the spacecraft:
At 01:56 UTC, Hayabusa2 released SCI, and JAXA officials said it should have been descending towards Ryugu at about 5 centimeters per second. SCI had a 40-minute timer, which means it should have dropped from 500 to 380 meters before detonation, meaning it was slightly higher than I had predicted in my What to Expect article!
Bad weather at JAXA's Usuda Deep Space Center forced Hayabusa2's signal over to NASA's Deep Space Network, apparently causing a slight delay in some of the telemetry received in the control room. Because of this, confirmation of SCI deployment, horizontal retreat, DCAM3 deployment, and vertical retreat all lagged slightly behind expected times, increasing the tension.
But confirmation eventually did come! After a short wait, JAXA confirmed everything went according to plan, and Hayabusa2 was receiving a signal from DCAM3 as it ducked behind Ryugu. Earlier in the broadcast, JAXA showed off a replica of DCAM3. It's very tiny!
Hayabusa2 was safe and sound, but what happened with SCI itself? The only way to confirm whether the explosives fired and created the artificial crater would be images from DCAM3, and a later search for the crater itself. DCAM3 transmitted a low-resolution analog camera signal to Hayabusa2 in real-time, while storing higher-resolution digital images for later. The camera had a 3-hour battery, giving it enough juice to send everything it captured back to Hayabusa2 before falling silent.
Later in the afternoon Japan time, JAXA showed off the first grainy photos from DCAM3, confirming that SCI worked!
[SCI] The deployable camera, DCAM3, successfully photographed the ejector from when the SCI collided with Ryugu’s surface. This is the world’s first collision experiment with an asteroid! In the future, we will examine the crater formed and how the ejector dispersed. pic.twitter.com/eLm6ztM4VX— [email protected] (@haya2e_jaxa) April 5, 2019
And in another tweet, JAXA said DCAM3 lasted 4 hours instead of 3!
At 16:04:49 JST we sent the command “Goodnight” to DCAM3. Images taken with the deployable camera will be a treasure that will open up new science in the future. To the brave little camera that exceed expectations and worked hard for 4 hours — thank you. (From IES兄) pic.twitter.com/1FBqncPrup— [email protected] (@haya2e_jaxa) April 5, 2019
The initial images JAXA released look to me like they were taken with DCAM3's analog cameras, so it's possible higher-resolution digital images could still be on the way (I haven't confirmed this). After Hayabusa2 returns to its home position in 2 weeks, it will descend to Ryugu for a closer look at the crater it created.
Here's one final picture: an image of the explosive-filled SCI package falling to Ryugu shortly after deployment. Hayabusa2 captured this using its optical navigation camera.