Saturn | Cassini Mission | Grand Finale

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

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Analemma On My Wall

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.


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Opportunity | Rover Enters Teenage

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.

Solar Transit | It Happened Again

Five days ago I received a notice that the space station would transit across the face of the Sun for my location. I wrote about a recent transit on 18 August 2016. I must be living right. The sky was clear again this time.

First view is in real time. Don’t blink. Duration of the transit is 0.94s. Second view is slowed to 10% of real time. For both, I suggest full screen. You might not see it on a phone or tablet.


What’s up for the rest of the month? This JPL video will tell you of some highlights.

Solar Transit | ISS Crosses the Sun

I’ve been waiting patiently. Today, three parts of a challenge finally came together. The sky was clear. I had the correct video equipment. And, the International Space Station crossed the face of the Sun as seen from my location. I received an email notice from CalSky this morning about this event. The track of the centerline was directly over our communities. I had to be ready in about an hour if I was to record video of the event.

I put the solar filter over the lens of my camera and put it on the tripod. I stepped outside to test the video settings. A test video of the Sun turned out as I hoped. I went inside and set a timer. The transit across the Sun was to occur moments after 1:03 local time. I figured to record from 1:02 until 1:04. The transit would show a silhouette of the ISS for only 0.6 seconds since it is going so fast at 5 mile/sec. I used my cell phone to accurately keep track of time. It was within a second of the national atomic clock.

Here is the result. The video is slowed down to half speed. Transit occurs about 6 seconds into it. You can slow it down even more with the gear tool on the video panel.


I was thrilled with the result. This isn’t the first time I’ve recorded a transit. Others are here and here. But, this is by far the best quality. I am still waiting for an opportunity to record an ISS transit of the Moon.

Here is a sequence of superimposed screen shots from the video showing a more detailed look at ISS. Two large solar array panels are quite visible. Total transit time was 0.6 sec. Each position of ISS is about 0.1 sec apart. Notice a few small sunspots left of center and to the far right limb. The faint concentric rings are imaging artifacts and not real. North is to the top of the frame.


Earth and Moon | A Different Viewpoint

Position a satellite camera 1 million miles from Earth directly toward the Sun, 4x the distance to the Moon. Keep it at that location and make it stare toward Earth. Eventually, this happens.


The Moon orbits Earth in a 5˚ tilted plane relative to Earth’s orbit plane. Rarely does the Moon pass directly between the camera location and the Earth. It happened twice in the past year. This pass was captured on 5 July 2016 by the camera on the satellite. It did so once before on 16 July 2015 shortly after the satellite became operational. The Moon passed behind Earth on 27 Sept 2015 as captured in this video. A solar eclipse was captured on 9 March 2016 as the umbra of the Moon’s shadow crossed the Pacific.

These views of Earth are provided by NOAA’s DSCOVR satellite. It is located at a point where the gravitational pull of Earth and Sun on the craft are equal and opposite. This stable location serves as an early warning site for geo-magnetic storms from the Sun. The Space Weather Prediction Center will begin using DSCOVR data on 27 July 2016 to monitor conditions and make predictions.

In much the same way distant off-shore sea buoys serve as early warning beacons for tsunamis, this satellite gives Earth 15-20 minutes of warning for solar storms that might affect Earth.



Recent true color views of Earth are available at this site. You can navigate forward and backward in time by clicking the right and left margins of the screen.

Scientists with the DSCOVR mission have compiled a video from over 3000 images of Earth taken by the EPIC camera on board during the year from July 2015 to July 2016. Notice how the tilt of the poles changes between summer and winter.


Astro-Images | Pillars of Creation

I’ve created color composites from three grayscale images using the technique in this post. The colors assigned are not necessarily what the human eye would see, but are used to bring out details. Unless otherwise noted, all images used three original grayscales from the Hubble Legacy Archive. Visit the gallery of previous Astro-Images.


NGC 6611 From ESO

The Eagle Nebula is about 7000 lt yrs distant in the constellation Serpens of the southern skies. The cluster of bright stars at the core was discovered by Jean-Philippe de Chéseaux in 1745-46. Images today show much more detail than Chéseaux was able to see. This image made from 3 greyscale components by the European Southern Observatory in 2009 shows those details. The very bright open cluster of stars barely right of center causes gases to glow and silhouettes of the dust regions. Those bright young stars formed 1-2 million yrs ago.

ESO | European Southern Observatory



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