Where is the Messenger Spacecraft right now?

The short answer to this question is: Messenger is on Mercury - where it crashed at the end of its mission on 30th April 2015.

The app above shows the trajectory of the Messenger Spacecraft and where it is right now. You can also wind the animation backwards in time to watch its launch and its successive flybys of the Earth, Venus and Mercury before entering Mercury Orbit in 2011.

Messenger Flight Path

Messenger was launched on the 3rd of August, 2004, with the aim of going into orbit around Mercury and studying this planet in more detail than ever before. The previous visit to the planet was the flyby of Mariner 4 a matter of 30 years before in 1975.

The idea of sending a probe to orbit Mercury had been evaluated before but it was considered too difficult/costly because of the problem of slowing the spacecraft down enough so that it matched the speed of Mercury closely enough. The problem is that as any craft falls into Mercury’s orbit it gains a lot of speed. In order to slow down in order to attain an orbit would require an enormous amount of fuel to decelerate. If Mercury had a thick atmosphere then the craft could possibly skim through the atmosphere to brake it, but Mercury's atmosphere is too thin for such a manoeuvre.

The problem was eventually solved by using a trajectory designed by Chen-wan Yen in 1985. This flight path involves using various flybys of the earth, Venus and Mercury so that gravitational sling shots (in reverse) would slow down the spacecraft sufficiently that much less fuel was required to achieve orbit.

The main manoeuvres are described here:

For an interesting 14 minute podcast about the Messenger Flight path and mission - visit the Physics Central website.

Orbit Insertion

This NASA animation shows the spacecraft entering Mercury Orbit.

The orbit is very elongated with Messenger passing between 200km from the surface to 15,000km every 12 hours. This allows the spacecraft to cool off since it gets hot passing so close to such a hot planet.

Mercury Image

Colour enhanced image of Mercury from Messenger. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Messenger has provided a huge amount of data and quite a few surprises. For a brief run down of discoveries, try this article.

Top Ten Discoveries

A quick review of the Messenger discoveries a month before mission end.

0:00 Preamble
3:00 Introduction
6:05 10. Field Aligned Currents (unexpected electrical flows within the planet)
7:05 9. Energetic Electrons (Successful detection of high energy electrons above Mercury -first detected by Mariner 10)
8:05 8. Dynamic Magnetosphere (smaller but 100x more dynamic than earths)
9:10 7. Seasonal Exosphere (Mercury's tenouous atmosphere is pushed out by the Sun into a huge tail, that fluctuates with Mercury's distance from the sun)
10:30 6. Global Contraction (Mercury is getting smaller at a faster rate than expected)
11:35 5. Volcanic Deposits (Messenger has gathered data on the history and variations of volcanic activity on Mercury)
12:40 4. Hollows (Strange features seen in craters which are geologically very young)
13:35 3. Offset Magnetic Field (Mecury's North and South magentic poles are located more to one side of the planet rather than directly opposite)
14:40 2. Solar Deposits (Confirmation that water Ice exists at the poles)
16:05 1. Volatile Rich Planet (The theories of planet formation have to be changed since Mercury has an abundance of volatile materials that were not expected to be available for planet formation so close to the Sun).
17:25 Handover
18:45 Engineering Top Ten Preamble
19:00 10. First Mercury Orbiter (and the complex flight path used to allow orbit insertion)
20:10 9. Economy of Space (Limitations on mass and power requirement (90W) for the entire spacecraft)
21:45 8. Sun Screen (Solutions to cooling, and also heating, the spacecraft)
23:05 7. Harnessing the Power (Operating solar panels in a heat intense environment)
23:55 6. No Side Dishes (The use of a phased array antenna rather than the usual parabolic dish)
25:00 5. SciBox (An application that helps planning data gathereing)
25:40 4. Fire Sale (Messenger was able to use its solar panels and heat shield as solar sails to perform trajectory adjustments without using rockets)
26:45 3. It Takes a Little Village (Acknowlegdement of the thousands of people involved in the mission)
27:30 2. Beyond the Last Drop (The clever use of residual helium gas pressure to prvide thrust when Messenger was out of fuel)
28:35 1. "Hovering" ( Low altitude passes over the planet).
30:00 Questions and Answers Begin.

Mission End

Messenger ran out of fuel and eventually crashed into Mercury as its orbit decayed. The mission was extended by using cold helium gas to give an additional thrust to the craft which extended the mission by a or more month. Article. Messenger finally crashed on the 30th April 2015.

More Information:

Messenger Mission
Messenger - Wikipedia