UPDATE (1:30 a.m. PT): A firehose of Cassini data has opened up and raw images of the spacecraft’s approach to the ring plane are coming in at a rapid pace. You can see the raw images appear online at the same time Cassini’s science team sees them here. At time of writing (and without any scientific analysis) the images have been of Saturn’s polar vortex and various views of the planet’s upper atmosphere. It’s going to take some time for more detailed views to become available, but, wow, it’s exhilarating to see Cassini images arrive at such a rate. Here are a few:
Original: As NASA planned, just before midnight on Wednesday (April 26), the veteran Cassini spacecraft made radio contact with the Goldstone 70-meter antenna in California, part of the Deep Space Network (DSN), which communicates with missions in space. Within minutes, Goldstone was receiving data, meaning the spacecraft had not only survived its first ring dive of the “Grand Finale” phase of its mission, but that it was also transmitting science data from a region of space that we’ve never explored before.
“We did it! Cassini is in contact with Earth and sending back data after a successful dive through the gap between Saturn and its rings,” tweeted the official NASA Cassini account just after the DSN confirmed it was receiving telemetry.
“The gap between Saturn and its rings is no longer unexplored space – and we’re going back 21 times,” they added.
Around 22 hours prior to Cassini’s signal, the spacecraft made its daring transit through the gap between Saturn’s upper atmosphere and innermost ring after using the gravity of Titan on Friday (April 21) to send it on a ballistic trajectory through the ring plane. But during that time the spacecraft went silent, instead devoting resources to carrying out science observations during the dive.
Of course there was much anticipation for Cassini to “phone home” tonight and it did just that right on schedule and now we can look forward to another 21 dives through Saturn’s rings before Cassini burns up in the gas giant’s upper atmosphere on Sept. 15, ending its epic 13 year mission at the solar system’s ringed planet.
“No spacecraft has ever been this close to Saturn before. We could only rely on predictions, based on our experience with Saturn’s other rings, of what we thought this gap between the rings and Saturn would be like,” said Earl Maize, Cassini Project Manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in a statement. “I am delighted to report that Cassini shot through the gap just as we planned and has come out the other side in excellent shape.”
So now we wait until images of this never-before-explored region of Saturn are released.
Imagine speeding down the highway and plowing into an unfortunate swarm of mosquitoes. Now imagine that you had the ability to precisely measure the mass of each mosquito, the speed at which it was traveling and the direction it was going before it exploded over your windscreen.
Granted, the technology to accomplish that probably isn’t feasible in such an uncontrolled environment. Factors such as vibration from the car’s motor and tires on the road, plus wind and air turbulence will completely drown out any “splat” from a minuscule insect’s body, rendering any signal difficult to decipher from noise.
The European LISA Pathfinder spacecraft is a proof of concept mission that’s currently in space, orbiting a region of gravitational stability between the Earth and the sun — called the L1 point located a million miles away. The spacecraft was launched there in late 2015 to carry out precision tests of instruments that will eventually be used in the space-based gravitational wave detector eLISA. Inside the payload is a miniaturized laser interferometer system that measures the distance between two test masses.
When launched in 2034, eLISA (which stands for Evolved Laser Interferometer Space Antenna) will see three spacecraft, orbiting the sun at the L1 point, firing ultra-precise lasers at one another as part of a space-based gravitational wave detector. Now we actually know gravitational waves exist — after the US-based Laser Interferometer Gravitational-wave Observatory (or LIGO) detected the space-time ripples created after the collisions of black holes — excitement is building that we might, one day, be able to measure other phenomena, such as the ultra-low frequency gravitational waves that were created during the Big Bang.
But the only way we can do this is to send stunningly precise interferometers into space, away from our vibration-filled atmosphere to stand a chance of detecting some of the faintest space-time rumbles in our cosmos that would otherwise be drowned out by a passing delivery truck or windy day. And LISA Pathfinder is currently out there, testing a tiny laser interferometer in a near-perfect gravitational free-fall, making the slightest of slight adjustments with its “ultra-precise micro-propulsion system.”
Although LISA Pathfinder is a test (albeit a history-making test of incredible engineering ingenuity), NASA thinks that it could actually be used as an observatory in its own right; not for hunting gravitational waves, but for detecting comet dust.
Like our mosquito-windscreen analogy, spacecraft get hit by tiny particles all the time, and LISA Pathfinder is no exception. These micrometeoroides come from eons of evaporating comets and colliding asteroids. Although measuring less than the size of a grain of sand, these tiny particles zip around interplanetary space at astonishing speeds — well over 22,000 miles per hour (that’s 22 times faster than a hyper-velocity rifle round) — and can damage spacecraft over time, slowly eroding unprotected hardware.
Therefore, it would be nice if we could create a map of regions in the solar system that contain lots of these particles so we can be better prepared to face the risk. Although models of solar system evolution help and we can estimate the distribution of these particles, they’ve only ever been measured near Earth, so it would be advantageous to find the “ground truth” and measure them directly from another, unexplored region of the solar system.
This is where LISA Pathfinder comes in.
As the spacecraft gets hit by these minuscule particles, although they are tiny, their high speed ensures they pack a measurable punch. As scientists want the test weights inside the spacecraft to be completely shielded from any external force — whether that’s radiation pressure from the sun or marauding micro-space rocks — the spacecraft has been engineered to be an ultra-precise container that carefully adjusts its orientation an exact amount to directly counter these external forces (hence the “ultra-precise micro-propulsion system”).
This bit is pretty awesome: Whenever these tiny space particles hit the spacecraft, it compensates for the impact and that compensation is registered as a “blip” in the telemetry being beamed back to Earth. After careful analysis of the various data streams, researchers are learning a surprising amount of information about these micrometeoroides — such as their mass, speed, direction of travel and even their possible origin! — all for the ultimate goal of getting to know the tiny pieces of junk that whiz around space.
“Every time microscopic dust strikes LISA Pathfinder, its thrusters null out the small amount of momentum transferred to the spacecraft,” said Diego Janches, of NASA’s Goddard Space Flight Center in Greenbelt, Md. “We can turn that around and use the thruster firings to learn more about the impacting particles. One team’s noise becomes another team’s data.”
So, it turns out that you can precisely measure a mosquito impact on your car’s windshield — so long as that “mosquito” is a particle of space dust and your “car” is a spacecraft a million miles from Earth.
NASA put together a great video, watch it:
Aside: So it turned out that I inadvertently tested the “car-mosquito” hypothesis when driving home from Las Vegas — though some of these were a lot bigger than mosquitoes…