Mars Odyssey to hear Curiosity in real-time

Courtesy of a successful readjustment of its orbit, the Mars Odyssey probe which has been orbiting the Red Planet for 11 years will be in the right position to relay Curiosity’s signals when the rover lands on 6 August 2012.

 

Curiosity is to land on Mars by means of a flying crane system! An innovation made necessary because of the rover’s significant mass: 900 kg. It is the biggest rover ever to be sent to the Red Planet (artist’s impression). Credit: NASA/JPL

 

In a previous article published on 18 July, we explained that due to technical problems there was a risk that the Mars Odyssey probe might remain on its current trajectory. This would then have meant that the venerable spaceship with its total of 11 years of good and loyal service orbiting the Red Planet would not have flown over Curiosity’s arrival area at exactly the right moment. Had Mars Odyssey arrived 5 to 10 minutes after the event, it would have delayed the relaying of the signal confirming the rover’s safe arrival by the same amount of time, thus creating additional suspense.

Delayed real-time
However, on 24 July, NASA and JPL (the Jet Propulsion Laboratory is managing the mission) announced that they had sent instructions to Mars Odyssey in order to enable the probe to perform an orbit correction. A highly successful operation (owing to the firing of a small thruster for 6 seconds) that “moved” Mars Odyssey 6 minutes along its path. The American Space Agency estimates that Mars Odyssey will now fly over Gale crater where Curiosity is due to land on 6 August such that it will be able to relay the rover’s transmissions “in real-time”.

The Mars Odyssey probe as it orbits Mars (artist’s impression). Credit: NASA/JPL

This notion of real-time does, however, need to be explained. JPL has calculated that Curiosity will land on Mars on 6 August at 07:18 French time (5 August at 22:18 at JPL headquarters in California). Therefore, at 07:18 French time on 6 August, Curiosity will transmit its first signal to indicate its safe landing without being able to send it directly to the Earth as our planet will have set a few minutes beforehand in relation to the area where the rover is to land. Fortunately, Mars Odyssey will fly over the rover and will retransmit its message to our planet (see diagram below). But, although this will take place in real-time, there is nevertheless a time delay of 13 minutes which is the time that the radio signal relayed by Mars Odyssey travelling at 300,000 km/s will take to cover the 248 million kilometres separating Mars from the Earth on 6 August. Hence, for ease of understanding we take this transmission delay into account (07:18 + 13 minutes) and say that the rover will land on Mars on 6 August at 07:31 French time; in short, delayed real-time even though Mars Odyssey is now "on time".

Credit: NASA/Enjoy Space

Follow Curiosity at the Cité de l’Espace and on the Internet
We would reiterate that the Cité de l’Espace is organising a special event for this milestone which is so important to the exploration of the solar system in general and of Mars in particular. The space adventure park in Toulouse is to open the doors of its Astralia building to the general public as of 06:30. NASA’s live video broadcast is to be retransmitted and a French commentary will be added on site by specialists so that big and small alike can follow the landing. Our special correspondent will provide additional information via live video from JPL in California. For those unable to travel to Toulouse, a live video stream is to be set up free-of-charge on Enjoy Space. In the meantime, you can already follow Curiosity via the regular information that is posted on the Twitter line; the most recent Tweets are shown below.



Twitter line @explorezmars

@explorezmars feature with a live video window on 6 August

Published on 25 july 2012