The astronomy community is active with posts and anticipation of the end of the Cassini Mission to Saturn early in the morning of 15 Sep 2017. This post serves as a brief reminder that you can witness the ending moments live by going online or via the NASA channel on cable. Set your calendar or clock.
Time to show up for the broadcast is 7 am Eastern Time, 6 CT, 5 MT, or 4 PT. I will leave the time calculation to others who live across the oceans.
Online sources include YouTube, NASA-TV, UStream, and Facebook. The table in the link includes links to each of those. You get to choose.
Consult your cable provider to see if they provide the NASA-TV channel.
For a huge number of links to current and past information about the Cassini Mission, please go to the Media Kit provided for reporters by NASA-JPL. It is loaded with terrific sources and deserves to be bookmarked for future reference beyond the end of this mission.
The Cassini-Huygens mission has delivered an enormous amount of new scientific findings about Saturn, its rings, and the surrounding many moons. Design work on the mission started in the 1980s as a joint effort by NASA, the European Space Agency ESA, and the Italian space agency Agenzia Spaziale Italiana ASI. Launch was on 15 October 1997. It reached Saturn orbit 1 July 2004 after flybys of Venus, Earth, and Jupiter to adjust the orbit speed and direction via gravity assist. My previous posts about many of the findings by Cassini and Huygens are listed here.
On 15 September 2017, the Cassini spacecraft ends the mission by plunging into the atmosphere of Saturn. It will not be left in orbit for fear of collision with a Saturnian moon and possible contamination of the moon. Future missions to the Saturn system need to be free of any potential contaminants from Earth.
Some scientists and mission specialists have worked on Cassini for their entire careers. This video highlights a few of them and how they feel about the legacy of the mission. I congratulate them all for a job well done. I will be watching NASA-TV at 6 am CDT September 15 to see the final moments of the plunge into Saturn. I hope you will be watching, too.
Iridium is a global network of communications satellites. The system was originally a product of Motorola. Iridium’s 66 satellites provide wireless mobile communications as they move in polar orbits at altitude of 485 mi (781 km). They are able to provide global coverage from pole to pole.
This brief video illustrates the ability of the constellation of satellites to receive a ground signal, pass it to other satellites, then deliver it to the ground in another part of the world.
The original Iridium satellites carry three highly reflective antennae as shown in the image below. Because of their mirror-like surfaces being positioned much of the time in intense bright sunlight, they sometimes reflect a bright spot of light to the ground. The ground track of the reflections is known precisely. If you happen to see it in the sky above, it grows in brightness over a few seconds and can be many times more intense that Venus and then it fades away. They are most easily seen just after sunset and before sunrise. They can also be seen in bright daylight if you know where to look.
Wikimedia | Cliff
I received an email earlier in the week telling me such a reflection, or Iridium flare, was to pass right over my house going south. In fact, another Iridium satellite in nearly the same orbit was to also flare me only 24 seconds after the first. The sky was clear the night of 13 May as I set up for a time exposure photograph.
About 45 seconds before 9:22:14 pm, I started the exposure using NightCap Pro on my iPad 2. The flare maximum occurred as predicted right on time. Coming right behind it was the next one. It passed and peaked at 9:22:38 pm. After 90 seconds I ended the time exposure.
Taken with NightCap Pro | ISS mode | 89.05 sec
How does one know when and where to look? I subscribe to a service called CalSky. It emails me when significant events like this are to occur. It offers many options and services but is not the easiest to use. There are others which are simpler. The best in my opinion for the general user is Heavens Above. In these services, you need to input your location. Heavens Above makes it easy to do by clicking on a map for your location.
Using the CalSky interface, I produced the sky chart of where the Iridium flares were going to pass. It gave this chart making it easy to know where to point my camera.
Saturn’s north pole features a hexagon shaped pattern in the clouds driven by fast winds that wrap the planet. The hexagon is about as wide as 2 Earths. This image taken by Cassini on 2 Apr 2014 is in greyscale.
On 26 Apr 2017, Cassini passed over this same hexagon region but at a much lower altitude. This pass was the first of 22 during the coming months in the Grand Finale of the mission. It will enter the cloud tops 15 Sep 2017 to end the 20 year mission at Saturn. As Cassini made this recent close pass, it imaged the hexagon in greyscale 3 time with filters of red, green, and blue.
Using Photoshop, I combined these RGB greyscale images into one with color. The colors are not necessarily what the eye would see. They are my choices in order to enhance differences in regions and appearance. The large blue object at the bottom is like the eye of a hurricane on Earth, but much larger.
The hexagon pattern can be produced in a laboratory evidenced in this post.
Launched 15 October 1997, the Cassini Mission is in its 20th year. It reached Saturn and entered orbit on 1 July 2004. Details of the mission can be read at this Wikipedia summary. This post is mostly about the maneuvers by Cassini to change its orbit and make 22 close encounters with Saturn in what is called the Grand Finale. End of mission is scheduled for 15 Sep 2017 when the spacecraft plunges into the atmosphere of Saturn ending a long and brilliant exploration of the famous ringed planet, its rings, and 62 moons.
Clean Room Workers Ready Spacecraft | NASA | 1996
Show me more…
A prism of high quality glass sits in a south window above our mantle. It is part of a surplus optical instrument from WW-II. The window crank gives a sense of its 2″x1″x1″ size.
When the Sun is low in the sky during late fall and winter, light through the prism casts a large full spectrum on the wall on the opposite side of the house. This is a closeup of the spectrum. It is always a delight to see the colors move slowly across the wall during the middle part of a sunny day.
Show me more…
On 24 January 2004, NASA’s Mars Exploration Rover Opportunity landed and started exploration. It joined the Spirit Rover which landed three weeks earlier on a different part on the Martian surface. The twin rovers were designed for mission lifetimes of 90 days.
Spirit’s last communication with Earth was 22 March 2010 more than six years into the mission. Opportunity is still operating well and continues to return images and data to Earth after thirteen years. It recently completed a marathon of distance travelled. Detailed maps are available here. To celebrate entering teenage, NASA Jet Propulsion Laboratory released this entertaining video about the milestone.