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.
It is important to look at the big picture. The way I see it, few people are aware of the sources of energy they utilize each day. Some energy is paid for directly such as gasoline for our cars. Gas for home heating, electricity for lights and air conditioning, etc. are often seen only as utility bills that come each month. What are the various energy sources we use?
Energy utilization was always an important topic in my physics classrooms. I wanted the students to know where their energy came from and how it was consumed by them and the general public. We discussed why efficiency was important. They were going to face and decide the actions on many complicated, technical, and politically charged issues in their future such as climate change. Those decisions would affect their quality of life and that of future generations.
We started with a simple flow diagram like the one below. The diagram shows how sources of energy are delivered to systems and devices that convert it into forms useful to the consumer. In the process, a useful amount of energy is delivered. But the conversions are never 100% efficient. As a result, much useless energy is wasted to the environment. We discussed examples of some common systems and how efficient they were. They soon got the point that increased efficiency and efforts to reduce wasted energy were actually very important issues. If we are unable to come up with more cheap sources, there are ways to reduce inefficiency and waste. Improved efficiency can be considered a source of energy and a lot of it. The diagram shows the gray box of Useless Wasted Energy quite large. It is actually much larger than the Useful Energy Output.
I follow the blog The Catholic Astronomer from the Vatican Observatory Foundation. I’ve heard of the Vatican Observatory for a long time but never knew much about it. It sits a above an extinct volcanic lake at Castel Gandolfo in the Papal Gardens near Rome.
Very recently, the observatory director and foundation director led a tour of the place. Joining them was Christopher Graney who is an astronomy teacher in Louisville, KY. He recorded videos for his class to see later. His videos are posted here on the blog site.
Scroll to the bottom of his post and click the left of three small images about the history and telescopes. His link will take you to the three videos.
One aspect of interest in the tour was of the women computers who worked there and their machine used to measure stars on the glass plates. It connected well with the work of the women computers in The Glass Universe by Dava Sobel. Those women laid the foundations for many of the important principles used in modern astronomy.
Venus presented a nice crescent this morning at about 6:30. She has passed the earth in orbit and will recede to a smaller diameter over the next few months.
Venus is closer to the Sun and orbits faster than Earth. Earth takes just over 365 days. Venus orbits in just under 225 Earth days. During the recent few months, Venus was bright and easily visible in the evening sky as it caught up to and passed Earth. In doing so, it came closer and appeared larger when viewed with a telescope or binoculars. This animation from a desktop program illustrates their motions. Mercury is not shown in order to simplify the view. The sizes are exaggerated.
I got my first morning view of Venus this spring at 6:45. There was a layer of high clouds to the east dimming the view quite a lot. Binoculars helped locate it for a photograph. Thanks to Scott at Scott’s Sky Watch for pointing out Venus is now visible both in the evening and the morning if the sky is clear enough. He called it a double dose of Venus.
There was another bonus this morning. Looking to the southeast, the waning crescent Moon shined through a clear break in the clouds.
How I saw Venus last evening. Only about one week until inferior conjunction. After that, Venus appears in the morning sky as a thin crescent.