In the current study, ten participants walked for two hours while carrying no load or a 40 kg load. During the second hour, treadmill grade was manipulated between a constant downhill or changing between flat, uphill, and downhill grades. Throughout the prolonged walk, participants performed two cognitive tasks, an auditory go no/go task and a visual target detection task. The main findings were that the number of false alarms increased over time in the loaded condition relative to the unloaded condition on the go no/go auditory task. There were also shifts in response criterion towards responding yes and decreased sensitivity in responding in the loaded condition compared to the unloaded condition. In the visual target detection there were no reliable effects of load carriage in the overall analysis however, there were slower reaction times in the loaded compared to unloaded condition during the second hour.

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This paper describes the design of a 10-channel infrared (1 .27 to 16.9 jim) radiometer instrument known as SABER (sounding of the atmosphere usingbroadband emissionradiometry) that will measure earth-limb emissions from the TiMED (thermosphere-ionospheremesosphere energetics and dynamics) satellite. The instrument telescope, designed to reject stray. light from the earth and the atmosphere, is an on-axis Cassegrain design with a clam shell reimager and a one-axis scan mirror. The telescope is cooled below 210 K by a dedicated radiator. The focal plane assembly (consisting of a filter array, a detector array, a Lyot stop and a window) is cooled to 75 Kby a miniature cryogenic refrigerator. The conductive heat load on the refrigerator is minimized by a Keviar support system that thermally isolates the focal plane assembly from the telescope. Kevlar is also used to thermally isolate the telescope from the spacecraft. Instrument responsivity drifts due to changes in telescope and focal plane temperatures as well as other causes are neutralized by an in-flight calibration system. The detectOr airay consists ofdiscrete IJgCdTe, JnSb and InGaAS detectors. Two InGaAS detectors are a new long wavelength type, made by EG&G, that have a long wavelength cutoffof2.33 im at 77 K.1. IPTRODUCTION SABER (sounding ofthe atmosphere using broadband emissionradiomelry) is an earth-limb-scanning radiometer that has been selected as one of the four payload instruments on TIMED (thermosphere-ionosphere-mesosphere energetics and dynamics) satellite to be launched in OctOber 1998. The TIMED orbit altitude is 600 km and the orbit inclination is 74.4 degrees. SABER will look 90 degrees to the ram. The mission life is 2 years.The SABER systems requirement review(SRR) and the conceptual design review (CoDR) were held in April 1 995, and the preliminaiy design review is scheduled for April 1996. Significant modifications to the SABER design described in the literature3 have been made in the last year. Many ofthese modifications resulted because the previous optical design required filters that were impractically thick to correct for chromatic focal shifts across the very wide spectral band covered by SABER. A new optical design that solved this problem and resulted in a much more rugged instrument was developed and is described in this paper. The stray light performance of this new design is excellent. This paper is intended to provide a comprehensive overview ofthe new SABER design. SYSTEM DESIGN -A functional diagram ofthe SABER instrument is shown in Figure 1. A high off-axis rejection telescope collects wanted light and discriminates against unwanted light. The scan mirror scans the instrument field ofview vertically across the earth limb. In orbit the telescope is oriented so the nadir_zenith line is vertical in Figure 1 and local depression angles are measured relative to the horizontal. The baffle opening allows the center of SABER's 1 .4 degree wide field ofview to be scanned across depression angles from 11.148 to 26.168 degrees. Thi...

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A one-dimensional mathematical model which simulates the dynamic performance of stratified solar brine ponds is described. The model simulates the upper convective zone, the middle nonconvective zone, and the lower convective zone. In addition to the energy flux, the model simulates the varying brine densities as a function of temperature and salt concentration, and thus is able to examine various pond stability criteria. On the basis of model operational studies, the following results are presented: (i) a study of overall pond efficiency in terms of the upper convective layer; (ii) an optimization study of the thickness of the nonconvective zone in terms of net energy transmission to the lower convective zone; (iii) an investigation of the heat storage efficiency and of the overall pond efficiency as a function of pond loading rate for a particular depth of storage zone.