Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 103E & 104E: Ballistic Capture & 3 PHAs Discovered In A Single Night
Organization: Travelers in The Night
Link : Travelers in the Night ; @Nmcanopus
Description: Today’s 2 topics:
- Spacecraft destined for Mars have so far used the Hohmann transfer to achieve an orbit about the red planet.
- In 3 1/2 hours Rose Matheny, discovered three PHAs with the Schmidt telescope on Mt. Bigelow. This string of catches should go into the Asteroid Hunting Guinness book of records.
Bio: Dr. Al Grauer is currently an observing member of the Catalina Sky Survey Team at the University of Arizona. This group has discovered nearly half of the Earth approaching objects known to exist. He received a PhD in Physics in 1971 and has been an observational Astronomer for 43 years. He retired as a University Professor after 39 years of interacting with students. He has conducted research projects using telescopes in Arizona, Chile, Australia, Hawaii, Louisiana, and Georgia with funding from NSF and NASA.
He is noted as Co-discoverer of comet P/2010 TO20 Linear-Grauer, Discoverer of comet C/2009 U5 Grauer and has asteroid 18871 Grauer named for him.
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Transcript:
103E: Ballistic Capture
Spacecraft destined for Mars have so far used the Hohmann transfer to achieve an orbit about the red planet. This approach requires the launch from Earth orbit to be in a small window in time which becomes possible every 26 months. When the spacecraft gets near Mars retro rockets, which require hundreds of pounds of fuel, must be fired to slow it so that the spacecraft so that it does not exceed orbital speed.
To make the trip to Mars orbit cheaper and more reliable a new technique has been theorized and then tested on Moon flights. It is called ballistic capture. The Japanese were first to use this method for a trip to the Moon in 1991. In this method a spacecraft is placed in a Mars like orbit, ahead of, and slightly slower than the red planet. As Mars overtakes the spacecraft it is naturally drawn into a highly elliptical orbit. This path can be modified into a better scientific orbit by skimming through Mars’s thin atmosphere. This maneuver, however, requires a heat shield which adds back some of the fuel weight saved compared to the Hohmann transfer technique.
Disadvantages of a ballistic capture trip include the fact that it may take a few months longer and it leaves the spacecraft 10 times higher than one which uses a Hohmann transfer. Advantages are that perhaps nearly twice the materials can be sent with the same amount of precious rocket fuel and the launch from Earth orbit can occur at anytime. This latter advantage would allow a steady stream of materials to be sent from Earth to help support a human colony on Mars.
104E: Three PHAs Discovered In A Single Night
In less than three and one half hours, my Catalina Sky Survey teammate, Rose Matheny, discovered three Potentially Hazardous Asteroids with the NASA funded, University of Arizona, Schmidt telescope on Mt. Bigelow. As far as I know, this string of catches should go into the Asteroid Hunting Guinness book of records.
A potentially hazardous asteroid is one which is larger than about 1.5 football fields in diameter and comes within 5% of the distance from the Sun to us. We keep special track of them since if one were to impact our home planet it would cause serious problems for human beings. We currently know about more then 1500 of these nearby, and possibly dangerous neighbors and discover a new one about every 4 days. Fortunately none of them are likely to hit the Earth in the foreseeable future.
Rose’s three new Potentially Hazardous Asteroids all orbit the Sun with periods ranging from 237 days to 2.6 years. They range in size from about 1.5 football fields to 0.4 miles in diameter. Two of them spend most of their time inside the Earth’s orbit about the Sun while the other one travels out to between Mars and Jupiter. When Rose discovered them they were opposite to the Sun with their little full Moon faces pointing towards us.
The Catalina Sky Survey operates 2 telescopes, 24 nights per month in the Catalina Mountains near Tucson, Arizona. Our goal is to provide an early warning should a celestial neighbor be on a collision course with planet Earth.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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