Posts Tagged ‘Comet Siding Spring’

12/29/2014 – Ephemeris – More events from 2014

December 29, 2014 Comments off

Ephemeris for Monday, December 29th.  The sun will rise at 8:19.  It’ll be up for 8 hours and 51 minutes, setting at 5:10.   The moon, 1 day past first quarter, will set at 2:32 tomorrow morning.

2014 has been a year of eclipses for northern Michigan.  A total lunar eclipse on the morning of April 15th, another on the morning of October 8th.  Plus we had a partial solar eclipse at sunset on October 23rd.  All of them were hampered by clouds, for this observer.  One of the cool events of this year was the close approach of Comet Siding Spring with Mars.  The five functioning orbiters and two rovers were not able to get any spectacular pictures of the comet, but there was one heck of a meteor shower on Mars when the planet was closest to the comet’s path.  None of the satellites could see it because they were hiding behind the planet at the time.  But later the martian atmosphere was filled with the chemical signatures of the meteors.

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


MAVEN detects metals

Metals in the atmosphere of Mars before and after the passage of Comet Siding Spring by Mars measured by the MAVEN spacecraft. Credit NASA.


11/18/2014 – Ephemeris – Rosetta, Philae with Comet 67P and Maven’s discovery of the effects of it’s comet encounter

November 18, 2014 Comments off

Ephemeris for Tuesday, November 18th.  The sun will rise at 7:43.  It’ll be up for 9 hours and 28 minutes, setting at 5:11.   The moon, half way from last quarter to new, will rise at 4:31 tomorrow morning.

Last week the Philae lander bounced down on Comet 67P/Churyumov-Gerasimenko, its harpoons not able to fire to hold the lander down.  “Where is Captain Ahab when you need him?” I Twittered at the time.  We were lucky it didn’t bounce off the comet entirely.  It ended against a cliff and in a shadow, so it couldn’t recharge its batteries from sunlight. The ESA controllers had it perform all its possible experiments quickly before its batteries died.  Philae was still an amazing success.  News from last month’s encounter Mars encounter with Comet Siding Spring. The Maven satellite detected the aftermath of a great martian meteor shower when it peaked around the planet from where it was hiding.

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



If I’m understanding the spacecraft controllers at the European Space Agency (ESA) correctly Philae was launched toward the comet with a velocity of something like .7 meters per second (m/s).  It would have accelerated to 1 m/s by the time it hit the comet.  So it was pushed into the comet at more than the comet’s escape velocity.  One meter per second is only 2.2 miles per hour.  So to bounce and not escape the comet either the lander, the surface of the comet or both would have to have a lot of give to it.  On this comet one could jump faster than escape velocity and go floating off into space.

Philae bounce

The Rosetta spacecraft spotted Philae and its shadow shortly after the lander touched down on Comet 67P/Churyumov–Gerasimenko and bounced up again. The first image is taken on Nov. 12, 2014 at 10:30 a.m. EDT (3:30 p.m. UTC) and the second five minutes later. Credit: ESA/Rosetta/NAVCAM; pre-processed by Mikel Catania. Hat tip to and credit for the caption to Universe Today.


Maven detected the aftermath of a meteor storm in the upper martian atmosphere with the signatures of eight metals.  It looks like it was prudent to hide all the satellites when Mars came closest to the comet’s path.  Here’s a link to Bob King’s post about it in Universe Today blog from 11 days ago.

10/16/2014 – Ephemeris – Comet Siding Spring will buzz Mars this Sunday

October 16, 2014 Comments off

Ephemeris for Thursday, October 16th.  The sun will rise at 7:59.  It’ll be up for 10 hours and 57 minutes, setting at 6:56.   The moon, 1 day past last quarter, will rise at 1:50 tomorrow morning.

Sunday afternoon our time the comet C/2013 A1 also known a Siding Spring will pass 86 thousand miles (140 thousand km) from Mars.  The three NASA Mars satellites, Mars Odyssey, Mars Reconnaissance Orbiter and Maven plus the two rovers Opportunity and Curiosity; the European Mars Express and the latest to arrive, India’s Mars Orbital Mission or MOM will all be studying the comet.  Protection of the satellites is key.  The satellite’s orbits have all been phased so as to be behind the planet from the expected possible debris of the comet when Mars passes its closest to the comet’s orbit 101 minutes after the comet itself passes.  Early next week we may have some spectacular photos of Comet Siding Spring.

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


Siding Springs Orbit

Two views of Comet Siding Springs orbit past Mars. Credit: NASA.

Planned science observations

Planned science observations of Comet Siding Spring by NASA spacecraft and rovers at Mars. Credit: NASA.

Siding Spring Links:

07/11/2014 – Ephemeris – Spot Mercury tomorrow and Learn about two comets tonight

July 11, 2014 Comments off

Ephemeris for Friday, July 11th.  Today the sun will be up for 15 hours and 19 minutes, setting at 9:27.   The moon, 1 day before full, will set at 6:31 tomorrow morning.  Tomorrow the sun will rise at 6:08.

Really diehard Mercury watchers just may catch a glimpse of this very elusive planet tomorrow morning after it rises at 4:47 a.m.  It’s below and left of Venus at that time.  But before then the Grand Traverse Astronomical Society will hold its monthly meeting tonight at Northwestern Michigan College’s Observatory on Birmley Road.  Yours truly will be giving the talk starting at 8 p.m. about the two comets that will be in the news starting next month.  The first will be orbited by the European Rosetta spacecraft which will send down a lander starting next month.  The second will be a close approach of a comet to Mars, near enough to possibly menace our satellites orbiting Mars in October.  There will be viewing afterwords.

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

More information on the talk is here.


Mercury and Venus

Mercury and Venus rising in twilight at 5:30 a.m. July 12, 2014. Created using Stellarium.

Title Slide

Title Slide for Tail of Two Comets

Tail of two comets

July 1, 2014 Comments off

It should be tale, but with apologies to Mr. Dickens I couldn’t resist. The two comets in question are 67P/Churyumov-Gerasimenko and C/2013 A1 (Siding Spring). Neither of these comets will come close to the Earth or be easily visible in telescopes, but they will be in the news starting next month.

Comet 67P/Churyumov-Gerasimenko

Comet 67P/Churyumov-Gerasimenko or Comet CG for short is a member of the Jupiter family of comets, more than likely captured into their current orbits by the king of planets. It is the target of European Space Agency’s (ESA) Rosetta Mission to orbit the comet for 17 months and deposit the Philae lander on the surface of the nucleus.

Rosetta was launched on March 2, 2004 on a long and complicated trajectory utilizing four planetary encounters to boost its orbit so it could match the comet, whose aphelion is near Jupiter’s orbit. Rosetta passed the earth a year after launch, then Mars in 2007, Earth again later that year and finally Earth two years later in 2009. On the way it entered the asteroid belt twice and passed by two asteroids: 2767 Šteins, 5 km in diameter, in 2008 and 21 Lutetia, 121 km along its longest dimension, in 2010.

Rosetta is solar-powered with enormous solar panels, yet it could not maintain it normal operations load when farther than 4.5 Astronomical Units (AU) from the Sun so controllers put the spacecraft in hibernation in May of 2011 with instructions to wake up and phone home on January 20, 2014. The signal came about a half hour late, but Rosetta woke up after 31 months in hibernation.

Rosetta is as of this writing (late June 2014) matching orbits with the comet. It’s out in front of the comet, and after two long rocket burns is slowing itself with respect to the sun and approaching the comet from its sun-ward side. Mission planners hoped to reach the comet before it becomes active, but the comet has surprised everyone by becoming active early. However the activity has stopped, as of mid June.

After four short thruster burns in July the velocity with respect to the comet will be down to 7.9 meters/second or 26 feet/second. And 4126 kilometers or 2,563 miles to go. Orbiting a comet nucleus only 2 X 3 miles across will be hard. The spacecraft’s orbital velocity in relation to it will be centimeters or inches per second. That will happen in August. A landing site for the Philae lander will be found as Rosetta spirals even closer to the comet.

With a landing site chosen the Philae lander will settle down on the surface of the nucleus in November by firing harpoons into the comet when it touches down to anchor it. The Philae lander, weighing approximately 220 pounds on Earth contains 10 instruments weighing 46 pounds which include cameras, organic molecule detector, isotopic ratio detector, magnetometer and plasma monitor, subsurface drill, and more.

The Rosetta orbiter will stay with the comet through the comet’s perihelion in December 2015, just outside the Earth’s orbit at 1.2 AU.

C/2013 A1 (Siding Spring)

Siding Spring was the first comet discovered in 2013. It raised headlines then because it could possibly crash into Mars in October 2014. The orbit has been refined, so the comet will miss by 83,000 miles or 134,000 km. On October 19th. The nucleus of the comet is estimated at somewhat less than a half mile in diameter. The comet’s coma or head has been measured to be 12.000 miles or 19,300 km across, though it’s sure to increase as it approaches closer to the sun. Hydrogen gas from the comet’s head or coma will possibly affect Mars’ upper atmosphere for a short time, increasing atmospheric drag on the five satellites then to be in orbit of Mars: NASA’s Odyssey, Mars Reconnaissance Orbiter, and Maven; ESA’s Mars Express, and India’s Mars Orbiter Mission or MOM.

The amount and spread of meteoric dust that would affect the satellites is unknown. Being a very long period comet, and possibly a first time visitor to the inner solar system, it may have very little dust and debris to menace the orbital armada now circling Mars. I have seen what ESA scientists are planning for their Mars Express satellite. They will, or have been tweaking their satellite’s orbit to be behind the planet when the peak of the meteoric material is expected. And since you can’t hide behind the planet forever, have looked at the design of the spacecraft, and decided to face the incoming meteoric stream with their antenna first. NASA has similar plans to duck their orbital assets behind Mars.

How do you change an orbit to duck behind a planet at a specific time? It’s the same technique for two space craft to rendezvous. One doesn’t want to change altitude too much. So to speed up a bit, drop into a slightly closer orbit of the planet. You do this by slowing down. It’s not quite intuitive. And the opposite is true to slow down. When the desired distance along the orbit is achieved reverse the process to get back to your original orbital altitude.

The Mars rovers Opportunity and Curiosity will be protected by Mars’ atmosphere. But could see some nice meteors, meteor shower or meteor storm. Curiosity, being nuclear powered can operate at night. I’m not sure if Opportunity has the power reserve.

This was originally printed in the Stellar Sentinel the July 2014 newsletter of the Grand Traverse Astronomical Society.


Links to my sources and more information:

ESA’s Rosetta mission

NASA’s Rosetta website

Comet Siding Spring Wikipedia page

NASA’s Comet Siding Spring at Mars site

ESA’s Mars Express blog posts on Comet Siding Spring