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Mars Pathfinder Current Position

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To those of you who have sent questions in your e-mail, I am working on responses. It may take me a while due to the large volume of e-mail I've received. Please be patient since I do intend to reply to all of your messages eventually. But if you get tired of waiting, check out Mars Team Answers Your Questions and see if you can find your question there.

Robin Vaughan, Mars Pathfinder navigator


new.gifWhat time is it on Mars? Check out the tables of local time on Mars at the Pathfinder landing site in the Mars Pathfinder Trajectory Data (Technical) Page. (This now include links to some other web sites with Mars time information.)


How far from Earth are Mars and the Pathfinder spacecraft? How far are they from the Sun? How fast are they going?


Date

Distance to Earth

Distance to Sun

Velocity
18 August, 1997 234737132.835 km 224129344.147 km 24.492 km/sec
145858892.092 mi 139267517.788 mi 54787.893 mph
19 August, 1997 235597209.546 km 223934024.682 km 24.480 km/sec
146393318.984 mi 139146151.899 mi 54760.380 mph
20 August, 1997 236452831.840 km 223738910.098 km 24.470 km/sec
146924978.028 mi 139024913.318 mi 54737.773 mph
21 August, 1997 237304064.957 km 223544031.835 km 24.463 km/sec
147453909.765 mi 138903821.579 mi 54722.070 mph
22 August, 1997 238150959.162 km 223349420.232 km 24.460 km/sec
147980145.427 mi 138782895.535 mi 54715.077 mph
23 August, 1997 238993548.404 km 223155104.169 km 24.461 km/sec
148503706.109 mi 138662153.131 mi 54718.353 mph
24 August, 1997 239831851.419 km 222961110.755 km 24.468 km/sec
149024603.453 mi 138541611.212 mi 54733.161 mph
25 August, 1997 240665874.225 km 222767465.063 km 24.480 km/sec
149542841.198 mi 138421285.358 mi 54760.431 mph
26 August, 1997 241495612.983 km 222574189.930 km 24.498 km/sec
150058416.959 mi 138301189.758 mi 54800.729 mph
27 August, 1997 242321056.571 km 222381305.816 km 24.522 km/sec
150571323.825 mi 138181337.126 mi 54854.240 mph
28 August, 1997 243142188.639 km 222188830.732 km 24.552 km/sec
151081551.638 mi 138061738.654 mi 54920.764 mph
29 August, 1997 243958989.174 km 221996780.243 km 24.587 km/sec
151589087.960 mi 137942404.013 mi 54999.717 mph
30 August, 1997 244771435.711 km 221805167.541 km 24.628 km/sec
152093918.833 mi 137823341.399 mi 55090.155 mph
31 August, 1997 245579504.361 km 221614003.578 km 24.672 km/sec
152596029.414 mi 137704557.620 mi 55190.800 mph
01 September, 1997 246383170.766 km 221423297.278 km 24.721 km/sec
153095404.566 mi 137586058.219 mi 55300.077 mph
This data is based on landing at latitude 19.28 degrees N and longitude 326.5 degrees E. Data is given for 12:00:00 Noon UTC on each date.

Now that the spacecraft is on the Martian surface, the distances in the table reflect the orbital motions of the Earth and Mars about the Sun. The velocity listed in the table is the velocity of the spacecraft relative to the Sun. This is a combination of Mars's orbital velocity as it revolves around the Sun and its rotational velocity as it spins around its axis every Martian day.

The information on Mars and Earth orbits used for this page is taken from the DE403 or DE405 planetary ephemerides developed by the Solar System Dynamics Group at JPL. For more information, see JPL Planetary and Lunar Ephemerides or HORIZONS.

If you'd like more technical details than are given here, please go to the Mars Pathfinder Trajectory Data (Technical) Page. new.gifThis now includes tables of local time on Mars at the Pathfinder landing site as well as information about our interplanetary cruise trajectory.


How did navigating Mars Pathfinder compare to a golf game? Check out these amazing facts about MPF navigation accuracy!

Curious about how our pre-landing navigation solutions mapped to our target landing area on Mars? See the landing footprint plots in the trajectory figures section of the Mars Pathfinder Trajectory Data (Technical) Page.

If you'd prefer to see the spacecraft location in a graphical form, plots are available in the trajectory figures section of the Mars Pathfinder Trajectory Data (Technical) Page. Orbital elements for Mars Pathfinder's cruise trajectory (from Earth to Mars) are also listed in the Mars Pathfinder Trajectory Data (Technical) Page.


mpfgolf.gif

When you play golf, you start by teeing off at the edge of a long green that's far away from a small hole in the ground. You get a certain number of shots to move your ball from the tee off point into the hole. You first try to get the ball to the green - another small area around the hole. If you're a good player, you figure you're home free once your ball is on the green. Surely you can make it to the hole from there!

Let's suppose that the tee off point for Mars Pathfinder navigation is the Earth at the time of launch in December 1996. And our "hole" is certain spot above the atmosphere of Mars on arrival day, July 4, 1997. We have two requirements for the accuracy with which we have to hit that spot above Mars. These are the criteria that determine the size of our "hole" and the size of the "green" around it that constitutes safe atmospheric entry conditions for the spacecraft.

Our safety and survival requirement for navigation is to get the spacecraft within a corridor that is 42 km (26 mi) wide centered at a radius of 3522.2 km (2189 mi) from the center of Mars at arrival. (For you technical types out there, this corresponds to a deviation in our nominal flight-path angle of +/- 1 degree.) We'll use 42 km (26 mi) as the diameter of our green. Our target zone on the surface is +/-100 km (62 mi) downtrack of a specified latitude and longitude. This corresponds to a corridor that is 24 km (15 mi) wide at the top of the atmosphere. We'll use this as the diameter of our hole.

Now the spacecraft will travel a total of 497418887 km (309081764 mi) from launch to arrival at Mars. (That's the distance measured along the spacecraft's trajectory - NOT the distance between Earth and Mars at launch or arrival or the distance from the spacecraft to Mars). Let's use that as the length of our golf course from tee off to the hole. A standard golf hole on Earth is 4 1/4 inches in diameter. Then, if we tee'ed off from JPL here in Pasadena, CA, the hole would be located on the outskirts of Houston, TX. And the safety requirement would be a green of 7 inches in diameter around the hole in Houston.

And if you're not bored with this analogy yet, we can go even further and say that our MPF navigation golf game is a "PAR 4". The 4 trajecory correction maneuvers that we planned between Earth and Mars are like strokes in the golf game. We'd like to make it onto the green - and into the hole - with just these 4 changes to the trajectory. We are carried the option for another (fifth) maneuver to be executed within the last 24 hours before arrival in case we had a bad game and need another stroke beyond the 4th.

The navigation team is happy to report that we made par! The fifth maneuver was not required and we successfully landed in the hole on July 4, 1997 :-)


Revision date: 16 August 1997

Robin Vaughan (rvaughan@mpfnav2.jpl.nasa.gov)

To those of you who have recently sent questions via e-mail, I am working on responses. It may take me a while due to the large volume of e-mail I've received since our landing on July 4th. Please be patient since I do intend to reply to all of your messages eventually. But if you get tired of waiting, check out Mars Team Answers Your Questions and see if you can find your question there.