Cassini Goes Where No Spacecraft Has Gone Before

For the probe, it’s one dive down between Saturn and its rings, 21 more to go before the end of its mission.

An artist’s illustration of Cassini between Saturn and the planet’s innermost rings
An artist’s illustration of Cassini between Saturn and the planet’s innermost rings (NASA / JPL-Caltech)

A few minutes before midnight in California, Cassini called home.

The spacecraft had been out of contact with Earth for about 41 hours, its large antenna pointed away from its home planet. This happens a few times a week as Cassini collects data around Saturn, fills up its recorders, and then turns back to stream the information across the solar system. But this stretch of silence was different. This time, after 13 years in Saturn’s orbit, Cassini was conducting a brand-new maneuver: diving into the narrow gap between Saturn and its innermost rings, a place where no spacecraft has gone before.

So scientists were relieved when Cassini pinged back.

“We had a very good night,” Earl Maize, the Cassini project manager at NASA’s Jet Propulsion Laboratory, wrote in an email at about 2:45 a.m. Thursday. “The flight team had actually built up to quite a bit of anticipation heading into tonight and was very excited to have the spacecraft come through its first dive through the gap unscathed.”

Raw data, including images, started flooding in shortly after midnight. Here’s one of the first look of the newly explored space:

During the dive, Cassini came within about 1,900 miles, or 3,000 kilometers, of Saturn’s cloud tops and within about 200 miles, or 300 kilometers, of the visible edge of the inner rings, according to JPL. The spacecraft then whipped back and away from Saturn, completing its elliptical orbit. The maneuver marked the final stages for Cassini, which is running out of fuel after two decades away from Earth. Cassini will conduct 21 more of these dives, about once each week, getting closer and closer to the planet each time until it burns up in its atmosphere in mid-September. The next dive is scheduled for May 2.

Maize said the team is working on analyzing the dust environment Cassini detected between Saturn and the rings. That was one of the main concerns going into this maneuver, whether the spacecraft would encounter particles from the rings that could damage its instruments or systems. Scientists predicted the floating ring material would be the size of smoke particles, but with Cassini traveling about 77,000 miles per hour, or 124,000 kilometers per hour, an impact with even a tiny speck could be harmful. For the maneuver, the team turned Cassini’s high-gain antenna, the 4-meter, white dish at the top of the probe, toward Saturn. The antenna acted like an umbrella, shielding the spacecraft as it approached the planet. The antenna has been deployed in this way dozens of times, Maize said, including when Cassini first entered Saturn’s orbit in 2004.

Maize and the team spent Wednesday getting some rest before a long night. The last time Maize donned a headset in mission control and waited for Cassini to call home was in 2005, when the spacecraft and dropped the Huygens probe on Titan, Saturn’s largest moon. After so many years working on Cassini, Maize said there was no way he was missing this moment in the spacecraft’s journey, another entrance into unchartered territory.

“When we do something like this, where the spacecraft has gone through a region that is unknown or slightly more challenging, then the silence is a little bit more apprehensive,” Maize told me Wednesday morning, while Cassini was silent. “Just because we want to hear back.”