Archive

Posts Tagged ‘Curiosity’

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.

Addendum

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

 

Advertisements

11/27/2012 – Ephemeris – What’s Curiosity’s big secret?

November 27, 2012 Comments off

Ephemeris for Tuesday, November 27th.  The sun will rise at 7:55.  It’ll be up for 9 hours and 10 minutes, setting at 5:05.   The moon, 1 day before full, will set at 7:53 tomorrow morning.

Last Tuesday NPR’s Joe Palca revealed that John Grotzinger the Principal Investigator for the Curiosity Rover mission on Mars had let slip that they may soon announce an earth shaking discovery.  The Jet Propulsion Laboratory and NASA have been backpedaling ever since.  The announcement may come next week Monday.  The discovery may have been made with the SAM instrument, the most complex chemical lab sent into space.  SAM is an acronym for Sample Analysis at Mars.  It is hoped that SAM might detect organic compounds.  Maybe it has.  The Viking missions in 1976 failed to detect organics.  It’s thought for organics to survive they would have to be below the surface shielded from the sun’s x-rays that get in through Mars’ thin atmosphere.

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

Addendum

Scoop marks at RockNest.  Image credit:  NASA/JPL-Caltech/Malin Space Science Systems

Scoop marks at RockNest. Image credit: NASA/JPL-Caltech/Malin Space Science Systems. Did the sample in question come from there?

When the Bad Astronomer Phil Plait posted his take on this last week.  I responded that I thought it was a discarded Earth Bar wrapper.   Think about it.

08/23/2012 – Ephemeris – A belated salute to Curiosity

August 23, 2012 Comments off

Ephemeris for Thursday, August 23rd.  The sun rises at 6:55.  It’ll be up for 13 hours and 38 minutes, setting at 8:34.   The moon, 1 day before first quarter, will set at 11:41 this evening.

It’s been two and a half weeks since the Curiosity Rover landed on Mars.  I finished the prior two weeks programs less than an hour before Curiosity landed and before heading off for vacation, so this is my first opportunity to talk about the landing.  The so-called “Seven Minutes of Terror” went without a hitch.  Either receiving transmissions directly from the spacecraft or through the Odyssey Mars orbiter, tones from the spacecraft ticked off the landing milestones right on time.  As I’m recording this Curiosity hasn’t moved, however it’s already zapped a rock with its laser, its delivered a panorama of its surroundings, and is still sending frames of the descent movie it took when the heat shield was dropped, until it touched down.

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

Addendum

Here’s a mix from the Seven Minutes of  Terror video created before landing cut with actual Jet Propulsion Laboratory (JPL) Mission Control footage as Curiosity actually landed.

Here’s another video of the landing cut with scenes of gatherings around the country including Times Square, and video from the landing imager and Curiosity descending on the parachute from the Mars Reconnaissance Orbiter.

Here is a hi-res descent and landing from the MARDI landing imager. Hat tip to the Bad Astronomer. Play at full screen for best effect.

Curiosity has Landed!

August 6, 2012 Comments off

Congratulations to JPL and NASA!

Categories: Mars, Space exploration Tags:

08/03/2012 – Ephemeris – Weekend events here and on Mars.

August 3, 2012 Comments off

Ephemeris for Friday, August 3rd.  The sun rises at 6:31.  It’ll be up for 14 hours and 32 minutes, setting at 9:04.   The moon, 2 days past full, will rise at 9:34 this evening.

The Northwestern Michigan College’s Rogers observatory will be open this evening starting at 9 p.m. For views of the heavens including the planet Saturn and the moon.  There’s some bright deep sky objects also visible.  Mars though up is a very tiny planet and is quite distant.  What can’t be seen in a telescope will be visible shortly.  Monday at 1:31 a.m. The Curiosity Mars Science Laboratory will land in Gale Crater.  If the landing is successful the new rover will be bringing a new arsenal of scientific instruments to probe the martian past.  From our vantage point on the earth Mars looks like a tiny yellowish orange disk.  We will be back to two operational rovers joining the three operational satellites now orbiting Mars.

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

Addendum

Here’s a movie from the Jet Propulsion Laboratory (JPL) of Curiosity’s entry descent and landing called Seven Minutes of Terror: http://youtu.be/ISmWAyQxqqs

07/03/2012 – Ephemeris – How Curiosity will land on Mars

July 3, 2012 1 comment

Ephemeris for Tuesday, July 3rd.  Today the sun will be up for 15 hours and 28 minutes, setting at 9:30.   The moon, at full today, will rise at 9:21 this evening.  Tomorrow the sun will rise at 6:03.

At 1:31 on the morning of August 6th our time the Curiosity Rover will land on Mars.  The entry, descent and landing of the rover will take just 7 minutes from first encountering the martian atmosphere.  The planning to land this nearly one ton lander on Mars was enormous.  There’s a heat shield to initially slow the spacecraft, then there is a parachute to slow it more.  It will be on the parachute for a maximum of 90 seconds.  Then 8 rockets will slow the rover more.  These are on the descent stage with the rover tucked underneath.  At the proper altitude the descent stage will lower the rover to the ground by cable, then fly off to crash some distance away.  This isn’t the half of it.  Check out the planetary dot org blog  section for more details.

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

Addendum

How Curiosity Will Land – Part 1

How Curiosity Will Land – Part 2

Youtube video:  “Challenges of Getting to Mars: Curiosity’s Seven Minutes of Terror”