Abstract: A satellite radiodetermination system comprises global navigation service (GNSS) satellites 2 such as GPS satellites, which generate GNSS ranging signals R.sub.n, geostationary satellites 6 which retransmit ranging signals R.sub.g generated at a navigation land earth station (NLES) 8, including augmentation data A, and medium earth orbit (MEO) satellites 10 which generate ranging signals R.sub.m including regional augmentation data RA transmitted from a satellite access node (SAN) 14. The regional augmentation data RA is supplied by regional augmentation systems 21a, 21b.A navigation receiver 11 receives the ranging signals R.sub.g, R.sub.m, R.sub.n and calculates ionospheric delay values for those ranging signals which are provided on dual frequencies. Using these ionospheric delay values, and optionally the regional augmentation data RA and the augmentation data A, the navigation receiver estimates ionospheric delay values for those ranging signals which are provided on single frequencies.

Abstract: The present invention provides a compact, highly automated photometric analyzer for measuring the concentration of substances found in a fluid, typically a blood sample or other body fluid sample taken from a patient. The operator places a small quantity of the sample into a special rotor and then loads the rotor into the analyzer. The analyzer accepts the rotor, centrifuges and dilutes the sample, and distributes the sample into a plurality of cuvettes near the outer edge of the rotor. Some of these cuvettes hold reagents which react with the sample. The analyzer then measures light absorption within the sample at a number of preselected frequencies. According to the present invention, a pair of specially designed apertures direct light from the sample through a plurality of beam splitters, interference filters, and associated photodetectors. The system also includes means for performing automatic calibration and error checking functions.