After 13 years and 77 days in orbit around Saturn, the Cassini spacecraft’s remarkable journey will come to a grand conclusion this week on Friday, Sept 15.
On Monday Sep 11, Cassini made a final pass around Titan, referred to as the “goodbye kiss”, and used Titan’s gravity to nudge its orbit slightly, so that the Cassini will plunge into Saturn’s atmosphere Friday morning. During its final hours, Cassini’s antenna will be pointed towards Earth, sending the last bits of science data in real-time until all systems go silent. The last signal from Cassini will reach Earth at 7:55 am EDT, 83 minutes after Cassini becomes one with the object of its admiration.
Since April 2017, Cassini has completed 22 dare-devil orbits that took its path through the gap between Saturn and its inner rings, studying Saturn and its rings from dangerously close proximity. In the graphic below, the 20 Ring-Grazing Orbits are shown in gray (Nov 2016 — April 2017); the 22 Grand Finale Orbits (since April 2017) are shown in blue. The final partial orbit is colored orange; Cassini has made the final turn around Titan (at 1:27 a.m. EDT Sep 12) and is headed for Saturn.
saturn.jpl.nasa.gov/… has a real-time display of the location and speed of Cassini. 1.225 million kilometers to go at 8:00 PM EDT Tuesday.
Here is a beautiful video from NASA on Cassini, its journey and the Grand Finale.
A few important milestones and accomplishments of Cassini, besides the awe-inspiring images of Saturn’s rings and moons -
Flight time to Saturn |
6 years, 259 days |
Duration at Saturn |
13 years, 77 days |
Moons discovered |
Methone, Pallene, Polydeuces, Daphnis, Anthe, Aegaeon and S/2009 S 1 |
Titan |
First probe landing on a moon in the outer solar system
Titan revealed as an Earth-like world with rain, rivers, lakes, seas (of liquid methane and ethane) and prebiotic chemistry
|
Enceladus |
Discovery of active, icy plumes on Enceladus |
Saturn’s rings |
Determined the three-dimensional structure and dynamic behavior of Saturn’s rings
|
Saturn’s poles |
First complete view of the north polar hexagon and discovery of giant hurricanes at both of Saturn's poles |
Jupiter |
Flyby and gravitational slingshot at Jupiter in Dec 2000. About 26,000 hi-res images of Jupiter, its faint rings, and its moons were taken during the six month flyby. |
Video of the Huygens probe descent and landing on Titan in 2005 -
There is an “astronomical” amount of information on Cassini, Saturn, its rings and moons. Explore the links in the references section below. And the plethora of recent articles on the subject.
What Next?
The Cassini mission, through its exploration of Titan and Enceladus, and its findings of water, organic molecules and local energy sources, has inspired strong interest in the exploration of "ocean worlds" among planetary scientists. See www.nasa.gov/… for more info.
A large number of missions to outer planets and their moons have been proposed and discarded for one reason or the other over the years. Here is a sample of the more recent planned missions and proposals -
Europa
Many lessons learned during Cassini's mission are being applied to planning NASA's Europa Clipper mission, scheduled for launch around 2022. Europa Clipper will be in orbit around Jupiter and fly by the icy ocean moon dozens of times to investigate its potential habitability. The Clipper mission orbit will be shaped by gravitational assists from its large moons to maneuver the spacecraft into repeated close encounters with Europa. This is similar to the way Cassini used the gravity of Saturn's moon Titan to continually shape the spacecraft's course.
ESA's Jupiter Icy Moons Explorer (JUICE) will fly-by Europa twice and Callisto multiple times before moving into orbit around Ganymede. JUICE will be launched around the same time as the Europa Clipper.
Another mission — the Europa Lander mission — is currently not being actively worked upon, due to lack of funding.
Saturn’s Moons
Cassini showed Titan and Enceladus to possess complex chemistry, that hold the promise of supporting life. Missions to explore Titan and Enceladus are high on the priority list, although there are no funded missions on the drawing board. Mission concepts under consideration include spacecraft to directly explore the methane seas of Titan and others to fly through the Enceladus plume to collect and analyze samples for signs of biology.
Here is a cool NASA video that shows a submarine concept to explore the liquid methane seas of Saturn's Moon Titan.
The Titan Saturn System Mission (TSSM), now on hold, is a joint NASA–ESA proposal for exploration of Saturn and its moons Titan and Enceladus. The mission would include a two-year Saturn tour, a 2-month Titan aero-sampling phase, and a 20-month Titan orbit phase. The TSSM mission consists of an orbiter and two Titan exploration probes: a hot air balloon that will float in Titan's clouds, and a lander that will float on one of its methane seas. The mission includes flybys of Enceladus and sampling of its cryovolcanic plumes.
The Enceladus Life Finder (ELF) is another proposed astrobiology mission to fly through and analyze Enceladus's geyser-like plumes. No lander or rover is included.
Outer Planets
A future mission to Saturn may include a probe that plunges through and explores Saturn’s atmosphere.
Uranus and Neptune, the "ice giant" planets, are objects of interest, due their difference in composition from gas-giant planets such a Jupiter and Saturn, characteristics that may be present in exoplanets outside the solar system.
A variety of potential mission concepts are discussed in a recently completed study, delivered to NASA in preparation for the next Decadal Survey -- including orbiters, flybys and probes that would dive into Uranus' atmosphere.
Remarks
Cassini will be missed by everyone — by scientists and non-scientists, by Saturn and its moons. It has fired the imagination of a generation of human beings in their quest to understand space, the solar system and our own origins.
However, we have barely scratched the surface in the exploration of our solar system, let alone celestial objects beyond. So many planets and their moons beckon and challenge us to send probes, landers and rovers to observe, analyze and understand up front and close, the mysteries of the universe and our place in it. Imagination, perseverance and human ingenuity are not in short supply, alas funding is.
References
- Cassini wiki — en.wikipedia.org/…
- Cassini home page at NASA — www.nasa.gov/...
- Cassini Quick Facts — saturn.jpl.nasa.gov/…
- Cassini image and video gallery at saturn.jpl.nasa.gov/…
- Saturn — en.wikipedia.org/…
- Moons of Saturn — en.wikipedia.org/...
- Ice Giants Mission Planning Studies — www.lpi.usra.edu/…
- Beyond Mars: 7 major proposed NASA and ESA missions to conquer the solar system and search for life — www.geektime.com/…
- Enceladus Life Finder proposal — www.lpi.usra.edu/…
- Europa Lander Study report — solarsystem.nasa.gov/...
- Enceladus - Plumes, Oceans, Hydrogen, Life? — www.dailykos.com/…
- NASA to Hold Media Call on Evidence of Surprising Activity on Europa — www.dailykos.com/...
P.S. NASA Webcast/TV schedule
From www.nasa.gov/… -
Wednesday, Sept. 13
- 1 p.m. EDT -- News conference from JPL with a detailed preview of final mission activities
Thursday, Sept. 14
- 10 a.m. to 3 p.m PDT -- NASA Social -- onsite gathering for 30 pre-selected social media followers (JPL-accredited media may also attend). Events will include a tour, and a speaker program that will be carried on NASA TV and online.
- After 2 p.m. PDT -- Media tours of Mission Control
- About 8 p.m. PDT -- Final downlink of images expected to begin (streamed online only)
Friday, Sept. 15: End of Mission
- 7 to 8:30 a.m. EDT -- Live commentary on NASA TV and online. In addition, an uninterrupted, clean feed of cameras from JPL Mission Control, with mission audio only, will be available during the commentary on the NASA TV Media Channel and on Ustream.
- About 8 a.m. EDT -- Expected time of last signal and science data from Cassini
- 9:30 a.m. EDT -- Post-mission news conference at JPL
For online streaming, visit: https://www.nasa.gov/live or www.nasa.gov/...
Prologue
On Sep 15 at 8:55 AM EDT, the last set of signals were received at the Canberra earth station from Cassini, which ended its long journey 83 minutes before.
The last set of signals from Cassini -
Leaving behind a proud legacy in space exploration and quite a few teary eyes here on Earth.