Cassini’s Final Five

Hard to imagine Cassini is about to begin the last five orbits of the mission. No mission extensions this time, Cassini will become part of Saturn.

The image is from 12 August 2014 credit: NASA/JPL-Caltech/Space Science Institute.

The Final Five from NASA:

NASA’s Cassini spacecraft will enter new territory in its final mission phase, the Grand Finale, as it prepares to embark on a set of ultra-close passes through Saturn’s upper atmosphere with its final five orbits around the planet.

Cassini will make the first of these five passes over Saturn at 12:22 a.m. EDT Monday, Aug. 14. The spacecraft’s point of closest approach to Saturn during these passes will be between about 1,010 and 1,060 miles (1,630 and 1,710 kilometers) above Saturn’s cloud tops.

The spacecraft is expected to encounter atmosphere dense enough to require the use of its small rocket thrusters to maintain stability – conditions similar to those encountered during many of Cassini’s close flybys of Saturn’s moon Titan, which has its own dense atmosphere.

“Cassini’s Titan flybys prepared us for these rapid passes through Saturn’s upper atmosphere,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory (JPL) in California. “Thanks to our past experience, the team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict.”

Maize said the team will consider the Aug. 14 pass nominal if the thrusters operate between 10 and 60 percent of their capability. If the thrusters are forced to work harder – meaning the atmosphere is denser than models predict – engineers will increase the altitude of subsequent orbits. Referred to as a “pop-up maneuver,” thrusters will be used to raise the altitude of closest approach on the next passes, likely by about 120 miles (200 kilometers).

If the pop-up maneuver is not needed, and the atmosphere is less dense than expected during the first three passes, engineers may alternately use the “pop-down” option to lower the closest approach altitude of the last two orbits, also likely by about 120 miles (200 kilometers). Doing so would enable Cassini’s science instruments, especially the ion and neutral mass spectrometer (INMS), to obtain data on the atmosphere even closer to the planet’s cloud tops.

“As it makes these five dips into Saturn, followed by its final plunge, Cassini will become the first Saturn atmospheric probe,” said Linda Spilker, Cassini project scientist at JPL. “It’s long been a goal in planetary exploration to send a dedicated probe into the atmosphere of Saturn, and we’re laying the groundwork for future exploration with this first foray.”

Other Cassini instruments will make detailed, high-resolution observations of Saturn’s auroras, temperature, and the vortexes at the planet’s poles. Its radar will peer deep into the atmosphere to reveal small-scale features as fine as 16 miles (25 kilometers) wide – nearly 100 times smaller than the spacecraft could observe prior to the Grand Finale.

On Sept. 11, a distant encounter with Titan will serve as a gravitational version of a large pop-down maneuver, slowing Cassini’s orbit around Saturn and bending its path slightly to send the spacecraft toward its Sept. 15 plunge into the planet.

During the half-orbit plunge, the plan is to have seven Cassini science instruments, including INMS, turned on and reporting measurements in near real time. The spacecraft is expected to reach an altitude where atmospheric density is about twice what it encountered during its final five passes. Once Cassini reaches that point, its thrusters will no longer be able to work against the push of Saturn’s atmosphere to keep the spacecraft’s antenna pointed toward Earth, and contact will permanently be lost. The spacecraft will break up like a meteor moments later, ending its long and rewarding journey.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL manages the mission for NASA’s Science Mission Directorate in Washington. JPL designed, developed and assembled the Cassini spacecraft.

The Total Solar and Spectral Irradiance Sensor

A VERY interesting mission about to get underway from a Space X rocket. The solar irradiance is a bit deeper than one might first surmise. Here’s a couple of companion links to the press release by NASA and Rani Gran:
NASA TSIS-1 website.
and
TSIS-1 Project website

A new instrument that will monitor our planet’s biggest power source, the Sun, arrived at NASA’s Kennedy Space Center in Florida. It has a targeted November 2017 launch on a SpaceX Falcon 9 rocket to the International Space Station. The Total Solar and Spectral Irradiance Sensor (TSIS-1) instrument was built by the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP) for NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Scientists will use TSIS-1 to study the Sun’s energy input to Earth. Specifically, it will measure both the total amount of light that falls on Earth, known as the total solar irradiance, and how that light is distributed among ultraviolet, visible and infrared wavelengths, called solar spectral irradiance.

We need to measure both because both affect Earth’s climate,” said Dong Wu, the TSIS-1 project scientist at NASA Goddard.

TSIS-1 will make these measurements with two sensors: the Total Irradiance Monitor and the Spectral Irradiance Monitor. These sensors advance previous measurements and are designed to see the tiny changes in solar irradiance, enabling scientists to study the Sun’s natural influence on Earth’s ozone layer, atmospheric circulation, clouds and ecosystems.

Scientists use the total solar irradiance measurements to quantify the variations in the Sun’s total amount of energy. Satellites have captured a continuous record of the total solar energy input to Earth since 1978, and have seen tiny fluctuations in solar energy output over the years. Most scientists believe the 0.1 percent variation in the Sun’s irradiance is too subtle to explain Earth’s recent warming, but it’s not impossible that long-term patterns proceeding over hundreds or thousands of years could cause more severe swings that could have profound impacts on climate. Scientists believe there could be a 100- or 200-year cycle of gradual heating up and cooling down periods for the Sun.

“We need to continue to monitor the Sun over longer periods during which the irradiance may change gradually but significantly,” said Peter Pilewskie, TSIS lead mission scientist from LASP in Boulder, Colorado. “How the atmosphere responds to subtle changes in the Sun’s output helps us distinguish between natural and human influences on climate.”

Scientists also study the solar spectral irradiance, the distribution of the Sun’s energy across its constituent wavelengths, because different wavelengths of light are absorbed by different parts of the atmosphere. For instance, the ozone layer is Earth’s natural sunscreen and protects life from harmful ultraviolet radiation. TSIS-1 measurements of the Sun’s ultraviolet radiation are critical to understanding the condition of this protective ozone layer.

Prometheus

A nice view of the tiny Saturn moon Prometheus and the wave in the F ring created by it’s gravitational wake that its gravity creates.

Have a look at our page about Prometheus.

The original caption:

The thin sliver of Saturn’s moon Prometheus lurks near ghostly structures in Saturn’s narrow F ring in this view from NASA’s Cassini spacecraft. Many of the narrow ring’s faint and wispy features result from its gravitational interactions with Prometheus (86 kilometers, or 53 miles across).

Most of the small moon’s surface is in darkness due to the viewing geometry here. Cassini was positioned behind Saturn and Prometheus with respect to the sun, looking toward the moon’s dark side and just a bit of the moon’s sunlit northern hemisphere.

Also visible here is a distinct difference in brightness between the outermost section of Saturn’s A ring (left of center) and rest of the ring, interior to the Keeler Gap (lower left).

This view looks toward the sunlit side of the rings from about 13 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 13, 2017.

The view was acquired at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn. Image scale is 4 miles (6 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Larsen C

I’ve seen a few different views of Larsen C and this image from ESA’s Sentinel-1 spacecraft is one of the best and arguably the most interesting.

ESA — On 12 July 2017, Europe’s Copernicus Sentinel-1 mission returned radar images showing that a lump of ice more than twice the size of Luxembourg had broken off the Antarctic Peninsula. Since then, this large tabular iceberg – known as A68 – has drifted about 5 km from the ice shelf. Images from Sentinel-1 also show that a cluster of more than 11 smaller icebergs has also now formed, the largest of which is over 13 km long. These ‘bergy bits’ have broken off both the giant iceberg and the remaining ice shelf. The image has been compiled using Sentinel-1 acquisitions on 27 July (right) and 30 July (left).

Image contains modified Copernicus Sentinel data (2017), processed by BAS–A. Fleming.

The Blue Streak Rocket

The Blue Streak developed by Britain started out as a military weapon in 1955. The military aspect of the programme was ended in 1960 and was reassigned to the European Launcher Development Organisation (ELDO) to launch satellites into orbit.

Britain pulled out of the ELDO in 1971, the last (British) Blue Streak programme launch was on 12 Jaunuary 1970 and the last ELDO Blue Streak launch being from French Guyana in 1971.

The entire ELDO project was canceled in 1973 and was replaced the the European Space Agency (ESA) we know today.

SPECTACULAR!

A breath taking image and great work from citizen scientists Gerald Eichstädt and Seán Doran using data from  the Juno spacecraft and publicly available at JunoCam. Fantastic job!!!!  Be sure to click the image for  the larger version.

NASA’s caption: A dynamic storm at the southern edge of Jupiter’s northern polar region dominates this Jovian cloudscape, courtesy of NASA’s Juno spacecraft.

This storm is a long-lived anticyclonic oval named North North Temperate Little Red Spot 1 (NN-LRS-1); it has been tracked at least since 1993, and may be older still. An anticyclone is a weather phenomenon where winds around the storm flow in the direction opposite to that of the flow around a region of low pressure. It is the third largest anticyclonic oval on the planet, typically around 3,700 miles (6,000 kilometers) long. The color varies between red and off-white (as it is now), but this JunoCam image shows that it still has a pale reddish core within the radius of maximum wind speeds.

Citizen scientists Gerald Eichstädt and Seán Doran processed this image using data from the JunoCam imager. The image has been rotated so that the top of the image is actually the equatorial regions while the bottom of the image is of the northern polar regions of the planet.

The image was taken on July 10, 2017 at 6:42 p.m. PDT (9:42 p.m. EDT), as the Juno spacecraft performed its seventh close flyby of Jupiter. At the time the image was taken, the spacecraft was about 7,111 miles (11,444 kilometers) from the tops of the clouds of the planet at a latitude of 44.5 degrees.

Plasma Sheet

The Sun is pretty energetic at the end of the solar cycle. This sheet of plasma above occurred on 28 July in about the same area that sunspot AR2665 is now. That sunspot, by the way, is the same one was associated with a very powerful CME on the far side of the Sun about a week ago.

There is a short video of the plasma sheet available from NASA.

NASA – A sheet of plasma blasted out into space from just behind the edge of the sun (July 28, 2017). While some material escaped into space, a portion of it was unable to break the pull of gravity and the magnetic forces nearby and can be seen falling back to the sun. The 3.5 hours of action was captured in a wavelength of extreme ultraviolet light.

Image: NASA/GSFC/Solar Dynamics Observatory

To Scale: The Solar System

A great video by Wylie Overstreet and Alex Gorosh.

I even do this every now and then myself just for fun and I get a bit of exercise in the process. I don’t do it quite the way Wylie and Alex did  as I just pace off this distances but even so, it is very interesting.

This is a GREAT activity for children!  Depending on what scale you use for distance you all you will need is a flat piece of ground, like say a football pitch. Even at one step per 10 million kilometers you can get a pretty long ways away from the starting point so plenty of room is helpful.

You can change the scale to fit your needs as long as you are looking at distance and not necessarily planetary sizes; also a good exercise for youngsters to exercise their brains during the school holiday.

To get you started have a look at this page from the Lunar and Planetary Institute.

ESA’s JUICE

This ‘family portrait’ shows a composite of images of Jupiter, including it’s Great Red Spot, and its four largest moons. From top to bottom, the moons are Io, Europa, Ganymede and Callisto. Europa is almost the same size as Earth’s moon, while Ganymede, the largest moon in the Solar System, is larger than planet Mercury.
While Io is a volcanically active world, Europa, Ganymede and Callisto are icy, and may have oceans of liquid water under their crusts. Europa in particular may even harbour a habitable environment.
Jupiter and its large icy moons will provide a key focus for ESA’s JUICE mission. The spacecraft will tour the Jovian system for about three-and-a-half years, including flybys of the moons. It will also enter orbit around Ganymede, the first time any moon beyond our own has been orbited by a spacecraft.
The images of Jupiter, Io, Europa and Ganymede were taken by NASA’s Galileo probe in 1996, while the Callisto image is from the 1979 flyby of Voyager.

The JUICE mission sounds like a typical ESA mission — ambitious and well planned.  It should be exciting, even if there is a long tome until launch.  Read more about the JUICE mission here.