Jennifer Herman

Thermoelectric microdevice fabrication process and evaluation at the Jet Propulsion Laboratory (JPL)

In the Materials and Device Technology Group at JPL, we have developed a unique fabrication method for a thermoelectric microdevice that utilizes standard integrated circuit techniques in combination with electrochemical deposition of compound semiconductors (Bi/sub 2/Te/sub 3//Bi/sub 2-x/Sb/sub x/Te/sub 3/). Our fabrication process is innovative in the sense that we are able to electrochemically micro mold different thermoelectric elements, with the flexibility of adjusting geometry, materials composition or batch scalability. Successive layers of photoresist were patterned and electrochemically filled with compound semiconductor materials or metal interconnects (Au or Ni). A thermoelectric microdevice was built on either glass or an oxidized silicon substrate containing 63 couples (63 n-legs/63 p-legs) at approximately 20 microns in structure height and with a device area close to 1700 /spl mu/m x 1700 /spl mu/m. In cooling mode, we evaluated device performance using an IR camera and differential thermal imaging software.

Mars Exploration Rovers 2004-2013: Evolving Operational Tactics Driven by Aging Robotic Systems

Over the course of more than 10 years of continuous operations on the Martian surface, the operations team for the Mars Exploration Rovers has encountered and overcome many challenges. The twin rovers, Spirit and Opportunity, designed for a Martian surface mission of three months in duration, far outlived their life expectancy. Spirit explored for six years and Opportunity still operates and, in January 2014, celebrated the 10th anniversary of her landing. As with any machine that far outlives its design life, each rover has experienced a series of failures and degradations attributable to age, use, and environmental exposure. This paper reviews the failures and degradations experienced by the two rovers and the measures taken by the operations team to correct, mitigate, or surmount them to enable continued exploration and discovery.

The Mars surface environment and solar array performance

January, 2010, marked the 6th anniversary for MER. This also marked the completion of more than three Martian years of solar array operation on Mars. During the spring of 2010, the MER rovers broke the RTG powered Viking Lander record for robotic operations on the Mars surface. Not only has a wealth of scientific information been obtained from MER but also a large quantity of data regarding factors that impact solar array performance. These include measurement of atmospheric dust, i.e., the atmospheric tau value. Additionally, dust buildup and removal from the solar array surfaces has been tracked. It is expected that the data from the rovers will enhance the prediction of future Mars surface solar array performance. Seasonal and annual trends have been identified. The results of these parameter analyses will be presented to assist in the design of future Mars surface solar power systems, both rover and stationary.

Managing PV power on Mars - MER Rovers

The MER Rovers have recently completed over 5 years of operation! This is a remarkable demonstration of the capabilities of PV power on the Martian surface. The extended mission required the development of an efficient process to predict the power available to the rovers on a day-to-day basis. The performance of the MER solar arrays is quite unlike that of any other Space array and perhaps more akin to Terrestrial PV operation, although even severe by that comparison. The impact of unpredictable factors, such as atmospheric conditions and dust accumulation (and removal) on the panels limits the accurate prediction of array power to short time spans.

Operations strategies for the Mars Exploration Rovers during the 2007 Martian global dust storm

In June and July 2007 Mars experienced a dust storm that grew to envelop all but the polar latitudes of the planet.1, 2 This dust storm was the first global dust storm to occur while the twin Mars Exploration Rovers (MER) began surface operations. It is estimated that the dust in the atmosphere prevented over 99.6% of direct sunlight from reaching the surface at the peak of the storm. Data collected indicated that solar array energy output was reduced to approximately 15% of maximum. The reduction in insolation and energy output posed the greatest risk of ending the mission for both rovers at that time.

Electrochemical Deposition of (Bi,Sb) 2 Te 3 for Thermoelectric Microdevices

The experimental techniques developed, as well as the transport properties of some of the films and filled templates, will be presented.

Strategic analysis for the MER Cape Verde approach

The Mars Exploration Rover Opportunity has recently completed a two year campaign studying Victoria Crater. The campaign culminated in a close approach of Cape Verde in order to acquire high resolution imagery of the exposed stratigraphy in the cliff face. The close approach to Cape Verde provided significant challenges for every subsystem of the rover as the rover needed to traverse difficult, uncharacterised terrain and approach a cliff face with the potential of blocking out solar energy and communications with Earth. In this paper we describe the strategic analyses performed by the science and engineering teams so that we could successfully achieve the science objectives while keeping the rover safe.