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The Telltale project

The Telltale is a passive wind indicator mounted on the NASA Phoenix lander, which landed on Mars in May 2008 and operated for 5 months. It was developed and constructed at the Mars Simulation Laboratory at the Aarhus University.

The Phoenix Lander

Phoenix landed on Vastitas Borialis close to the North Pole of Mars on May 25, 2008. In this region, ice had been detected in the soil by means of a gamma ray spectrometer (GRS) and a neutron spectrometer on board the NASA Mars Odyssey orbiter. The Phoenix lander dug for samples and delivered them to various chemistry experiments on the lander deck. Having crude information on the wind cycle at the landing site, it was possible to select times for delivery of samples where the dust was not just blown away in the wind.

The Telltale

The Telltale consists of a gallow that is mounted on top of the meteorological mast of the Lander. The active element of the instrument is an extremely lightweighted Kapton tube hanging in Kevlar fibers. Images taken of the instrument show the deflection of the Telltale due to the wind. A mirror is mounted below the active part to enable derivation of better information about the direction of deflection of the moving part of the Telltale.

Telltale history

The Telltale was developed, constructed and delivered at extremely short time compared to what is usually the case with scientific equipment for planetary missions. In April 2005, only a concept of the experiment existed, and in February 2007, the flight unit of the Telltale was delivered fully tested and calibrated. In the meantime, the team experienced failed tests and redesigning of the experiment.

After the landing on Mars in May 2008, data collection was initiated at the Science Operations Centre at University of Arizona in Tucson, Arizona. During the summer, the Telltale team worked on analysing the incoming data from Mars to determine wind speeds and directions. It was a help in classifying the diurnal wind cycle and supporting sample delivery to other instruments on the Phoenix lander.

An example of wind speed data collected by the Telltale during the mission is seen here. What is shown in the figure is the average wind speed throughout the duration of the mission.

Animated gif showing a series of 5 pictures taken within an 8 minute time period on Mars. The pictures were taken on Sol 8, the eighth day of the mission, just after 1300, local solar time.