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05/28/2018 – Ephemeris – NASA’s Juno spacecraft takes deep dives at Jupiter

May 28, 2018 Comments off

Ephemeris for Memorial Day, Monday, May 28th. Today the Sun will be up for 15 hours and 15 minutes, setting at 9:17, and it will rise tomorrow at 6:02. The Moon, 1 day before full, will set at 6:24 tomorrow morning.

NASA’s Juno spacecraft has made 11 close passes of Jupiter since being inserted into Jovian orbit in July 2016. It has a highly elliptical orbit. It comes in over the north pole, passes only 2,000 miles over the cloud tops at the equator and heads out over the south pole, avoiding the most intense parts of Jupiter’s radiation belts. The high latitude and polar clouds appear more chaotic than expected. We can’t see these very well from the Earth. The magnetic field is much stronger and lumpier than thought before. A very much improved and complex picture of our largest planet is emerging, as we expected. The mission isn’t over and years of analysis are ahead to begin to more fully understand the solar system’s greatest planet.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addenda

Chaotic storms at Jovian high latitudes

Chaotic storms at Jovian high latitudes. Credit NASA/JUNO

North Polar Cyclones

Jupiter’s North Pole in the infrared. 8 cyclones surrounding a 9th at the pole. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

South Polar Cyclones

Jupiter’s South Pole in the infrared. 5 cyclones surrounding a 6th at the pole. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

Alan Bean

Astronaut Alan Bean, 4th person to walk on the Moon with Apollo 12 passed away this weekend.  He also commanded the second Skylab mission and retired to become an artist, a painter of his adventures on the Moon and in space.  Of the twelve men who walked on the Moon, only four survive.

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10/03/2017 – Ephemeris – OSIRIS-REx and the asteroid Bennu

October 3, 2017 1 comment

Ephemeris for Tuesday, October 3rd. The Sun will rise at 7:43. It’ll be up for 11 hours and 35 minutes, setting at 7:18. The Moon, 2 days before full, will set at 6:11 tomorrow morning.

Eleven days ago, on September 22nd, a small spacecraft named OSIRIS-REx zipped past the Earth to gain speed and alter the inclination of its solar orbit to reach the asteroid Bennu late next year. Bennu is rated as a potentially hazardous asteroid, with a tiny chance of colliding with the Earth late in the next century.

Discovered in 1999, and named by a 9-year-old boy in a contest run by the Planetary Society after an Egyptian god who is depicted as a heron, because the spacecraft kinda looked like one. It is a carbonaceous asteroid, containing very primitive material from the dawn of the solar system. OSIRIS-REx will take a sample of the asteroid and return it to the Earth in 2023 if all goes well. The Earth pass also allowed it to calibrate its instruments.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

OSIRIS-REx

Artist’s conception of OSIRIS-REx about to collect a sample from asteroid Bennu. Image Credit:
NASA/Goddard/Chris Meaney

Earth flyby

OSIRIS-REx observes the Earth. Here is the Pacific Ocean with Australia at the lower left, and the western US and Baja California at the upper right. Credit: NASA’s Goddard Space Flight Center/University of Arizona

NASA’s caption:  A color composite image of Earth taken on Sept. 22 by the MapCam camera on NASA’s OSIRIS-REx spacecraft. This image was taken just hours after the spacecraft completed its Earth Gravity Assist at a range of approximately 106,000 miles (170,000 kilometers). MapCam is part of the OSIRIS-REx Camera Suite (OCAMS) operated by the University of Arizona. Visible in this image are the Pacific Ocean and several familiar landmasses, including Australia in the lower left, and Baja California and the southwestern United States in the upper right. The dark vertical streaks at the top of the image are caused by short exposure times (less than three milliseconds). Short exposure times are required for imaging an object as bright as Earth, but are not anticipated for an object as dark as the asteroid Bennu, which the camera was designed to image.

Categories: Ephemeris Program, NASA Tags: ,

09/14/2017 – Ephemeris – Cassini will go out in a blaze of glory tomorrow morning

September 14, 2017 2 comments

Ephemeris for Thursday, September 14th. The Sun will rise at 7:20. It’ll be up for 12 hours and 33 minutes, setting at 7:54. The Moon, 1 day past last quarter, will rise at 2:05 tomorrow morning.

Just about 24 hours from now the Cassini spacecraft will end its 20 year mission to Saturn and its 13 years of orbiting the planet. Monday, 4 days ago, it passed the great moon Titan for the last time, giving it one last gravitational boost into a suicidal plunge into Saturn’s atmosphere. At 7:55 tomorrow morning EDT (11:55 UTC), Cassini is expected to lose its stabilization in the thin upper atmosphere or Saturn and lose its connection with the Earth. It is expected to burn up, traveling at 70,000 miles an hour to become a part of the planet it investigated for 13 years. Instead of recording data for transmission to Earth later, it will be taking real-time atmospheric sampling, transmitting immediately up to the very end.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini in the gap

An artist’s visualization of Cassini slipping between the rings and the atmosphere of Saturn. Credit NASA/JPL.

Here’s a link to yesterday’s news conference at JPL on the end of the Cassini Mission:  https://youtu.be/gs-dscW95PE.

Link to Emily Lakdawalla’s Planetary Society post on the final days of Cassini including NASA TV coverage:  http://www.planetary.org/blogs/emily-lakdawalla/2017/0911-cassini-eom-timeline.html.

09/04/2017 – Ephemeris – Cassini has only 11 days to go.

September 4, 2017 Comments off

Ephemeris for Labor Day, Monday, September 4th. The Sun will rise at 7:08. It’ll be up for 13 hours and 4 minutes, setting at 8:13. The Moon, 2 days before full, will set at 6:16 tomorrow morning.

In 11 days, the school bus sized Cassini spacecraft, which has orbited Saturn for the last 13 years will make it’s final plunge into Saturn’s atmosphere to burn up. Cassini’s controllers at the Jet Propulsion Laboratory decided after finding the small moon Enceladus had an internal ocean that it was venting into space with interesting compounds, that it could possibly harbor life, so leaving Cassini derelict orbiting Saturn among the moons, was thought not to be a good idea, in case the unsterilized spacecraft were to crash into Enceladus. So since this spring Cassini was directed to make a series of orbits that took it inside the rings, and on the final orbit to plunge into Saturn’s atmosphere to burn up.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini Flying between the planet and the rings.

An artist’s visualization of Cassini Flying between the planet and the rings. Credit NASA/JPL.  Click on the image to enlarge.

05/11/2017 – Ephemeris – Cassini is surviving its death-defying dives under the rings of Saturn

May 11, 2017 Comments off

Ephemeris for Thursday, May 11th.  Today the Sun will be up for 14 hours and 40 minutes, setting at 8:59, and it will rise tomorrow at 6:17.  The Moon, 1 day past full, will rise at 9:42 this evening.

The Cassini spacecraft has been redirected by passing Titan on a special trajectory that sent it into a fatal set of orbits that take it a few thousand miles above Saturn’s cloud tops and under the innermost rings.  So far after two passes Cassini survives.  One discovery of the first pass was a storm, perhaps a hurricane, whose clear eye is at Saturn’s north pole.  Cassini has yet to turn its cameras to the rings on these passes inside the rings, but it will before its final orbit.  Currently it is flying communication dish first to protect its delicate instruments from ring particles.  So far the gap between the rings and the planet are more free of particles than expected.  Which is a good omen for the last 20 passes between the rings and planet.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini's grand finale

In its planned last 22 orbits of Saturn, the Cassini spacecraft will pass between the innermost ring and the planet itself. Credit NASA, JPL.

Saturn's North Pole

The clearing (blue sky) in the clouds at Saturn’s north pole spotted by Cassini on its first pass under the rings. Credit: NASA/JPL-Cal Tech/S Si/Sophia Nasr

 

04/25/2017 – Ephemeris – The Cassini spacecraft is on its last 22 orbits of Saturn

April 25, 2017 2 comments

Ephemeris for Tuesday, April 25th.  The Sun rises at 6:41.  It’ll be up for 13 hours and 58 minutes, setting at 8:40.  The Moon, 1 day before new, will rise at 7:08 tomorrow morning.

In the early hours of last Saturday, Earth Day, The Cassini spacecraft, orbiting Saturn for the last nearly 13 years, made its last pass of Saturn’s giant moon Titan.  Over the past 13 years Cassini has been using Titan as a kind of fulcrum to leverage its orbits of Saturn, returning time and time again to both study this strange moon and to propel it via gravity assists into a myriad of orbits.  This time however, with one last gravitational assist, Cassini was flung into a series of 22 daring orbits which will take it into a couple of thousand mile gap between the rings and the planet.  On orbit 22, if it doesn’t collide with an errant ring particle, Cassini will burn up in Saturn’s atmosphere, going something like 70,000 miles an hour on September 15th.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini's grand finale

In its planned last 22 orbits of Saturn, the Cassini spacecraft will pass between the innermost ring and the planet itself. Credit NASA, JPL.

04/11/2017 – Ephemeris – What’s under Jupiter’s cloud tops?

April 11, 2017 Comments off

Ephemeris for Tuesday, April 11th.  The Sun will rise at 7:04.  It’ll be up for 13 hours and 17 minutes, setting at 8:22.  The Moon, at full today, will rise at 8:54 this evening.

I made an error in yesterday’s on-air program which I fixed before posting this blog version.  The moon Io will be over the face of Jupiter from when it rises tonight until 8:58 p.m.*, thereafter it will be seen just to the west of the planet.  What we see of Jupiter are its cloud tops.  Planetary astronomers have some very educated guesses as to what lies beneath them.  An atmosphere of mainly hydrogen and helium, ending in a hot liquid ocean of hydrogen.  Beneath that a core of metallic hydrogen that generates the planet’s huge magnetic field.  Below that maybe a core of solid iron and other metals.  NASA’s Juno spacecraft now orbiting Jupiter is tasked with finding out the interior structure by measuring the velocity of the spacecraft as it flies just above the cloud tops of this giant planet.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

* Observers in other locations around the world can check out the table from yesterday’s post of other Jovian satellite events after this entry is posted at 4:01 UT, April 11, 2017.

Addendum

Jupiter on two nights

Jupiter and its moons in a telescope at 10 p.m. both April 10th & 11th, 2017. Created using Cartes du Ciel (Sky Charts).

For a year’s worth of Jovian satellite events and when the Great Red Spot crosses Jupiter’s central meridian, go to: http://www.projectpluto.com/jevent.htm.

Juno Spacecraft

The Juno spacecraft. Credit: NASA.

Jupiter's south pole

A February 2, 2017 Juno image of Jupiter’s south pole and its chaotic storm clouds. I think I have a paisley tie that looks like that. Credit NASA/JPL-Caltech/SwRI/MSSS/John Landino.