Physics Colloquia at CSUF

Dr. Bruce Banerdt, NASA Jet Propulsion Laboratory, California Institute of Technology.
April 6, MH121, 1pm

Title: "Probing the Ancient Environment of Mars with Spirit and Opportunity"
Abstract:
NASA launched two robotic geologists, Spirit and Opportunity, toward Mars in June and July of 2003, reaching Mars the following January. Although they were designed for a 90-day mission, both rovers have lasted more than three years on the surface and each has covered more than four miles while gathering evidence on ancient environmental conditions on Mars.

The science objectives for this mission are focused on delineating the geologic history for two locations on Mars using geological and geochemical techniques. There is a strong emphasis on the history of water, as it is a unique ingredient in a broad variety of processes. Instruments include high-resolution cameras (both panoramic and close-up), a thermal infrared spectrometer, an alpha particle/X-ray spectrometer, and a Mossbauer spectrometer.

Spirit was targeted to Gusev Crater, a 300-km diameter impact basin that was suspected to be the site of an ancient lake. Initial investigations of the plains in the vicinity of the landing site found no evidence of such a lake, but were instead consistent with unaltered (by water) basaltic plains. But after a 3-km trek to an adjacent range of hills it found a quite different situation, with abundant chemical and morphological evidence for a complex impact, volcanic, and hydrothermal history.

Opportunity has been exploring Meridiani Planum, which was known from orbital data to contain the mineral hematite, which generally forms in the presence of water. The rocks exposed in Meridiani are highly chemically altered with abundant sulfur, and appear to have been exposed to significant amounts of water. By descending into the 130-m diameter Endurance Crater, Opportunity was able to analyze a 10-m vertical section of this rock unit, which showed significant gradations in chemistry and morphology. More recently, it completed an 8 km trek to the edge of the much larger (800 m) Victoria Crater, and is preparing to descend into its interior.

Dr. Wayne Lau, University of California Santa Barbara
Wednesday, April 18, MH 606, 4pm

Title: TBA


Dr. Bernardo Jaduszliwer , Principal Director, Electronics and Photonics Laboratory, The Aerospace Corporation.
Friday, April 27, MH121, 1pm
Title:"GPS, TIME AND ATOMIC CLOCKS".
Abstract:
The Global Positioning System (GPS), conceived by the USAF as a military positioning and navigation satellite system in the 1960's, became fully operational in the 1990's and by now it has become a worldwide utility, as much a part of everyday modern life as cell phone communications or the availability of hundreds of TV channels. If imitation is the best form of flattery, GPS is being flattered indeed: GLONASS (Russian) and Galileo (European Community) have been architected following very closely the GPS model. But the current pervasiveness of GPS (and other Global Navigation Satellite Systems, or GNSS) should not hide the fact that they truly challenge current technology.

At the heart of each GNSS spacecraft there is an atomic clock, and the timekeeping performance of those clocks ultimately determines the positioning accuracy of the system. My talk will give a brief introduction to GNSS, discuss how to characterize atomic clock performance, and describe the general physical principles used in their design. I will then discuss in some more detail the specific clock technologies used in current and near-future GNSS.