Fredrick Solheim

• PhD Geophysics University of Colorado 1993
• CEO at Dakota Ridge R&D

Radio-frequency interference (RFI) can significantly contaminate the measured radiometric signal of current spaceborne L-band passive microwave radiometers. These spaceborne radiometers operate within the protected passive remote sensing and radio-astronomy frequency allocation of 1400–1427 MHz but nonetheless are still subjected to frequent RFI in...

Radio Frequency Interference (RFI) can significantly contaminate the measured radiometric signal of current spaceborne L-band passive microwave radiometers. These spaceborne radiometers operate within the protected passive remote sensing and radio astronomy frequency allocation of 1400–1427 MHz, but despite this are still subjected to frequent RFI...

NASA has teamed with the FAA, DoD, industry, and academia for research into the remote detection and measurement of atmospheric conditions leading to aircraft icing hazards. The ultimate goal of this effort is to provide pilots, controllers, and dispatchers sufficient information to allow aircraft to avoid or minimize their exposure to the hazards...

A microwave radiometer is described that provides continuous thermodynamic (temperature, water vapor, and moisture) soundings during clear and cloudy conditions. The radiometric profiler observes radiation intensity at 12 microwave frequencies, along with zenith infrared and surface meteorological measurements. Historical radiosonde and neural netw...

Thermodynamic profiling provides continuous temperature, humidity and cloud liquid profiles during clear and cloudy conditions. The thermodynamic profiler radiometrically observes microwave radiation intensity at multiple frequencies, along with infrared and surface meteorological measurements. Historical radiosonde and neural network or regression...

Radiometric profiling provides accurate and reliable temperature and humidity profiles up to 10 km height, and low resolution cloud liquid profiles. Retrieval algorithms are derived for specific locations using historical radiosonde data and neural network or regression analysis. Radiometric profiler measurements can be used for high resolution mes...

We describe a passive microwave radiometer that provides continuous unattended atmospheric temperature and humidity profiles up to 10 km in height, and low resolution liquid water profiles. Profile accuracies in cloudy and clear conditions up to 7 km height are better than 2.5 K (temperature) and 1.1 g/m3 (humidity) as determined by statistical com...

Dry air, water vapor, hydrometeors, and other particulates (sand, dust, aerosols, and volcanic ash) in the atmosphere introduce microwave propagation delays. These delays must be properly characterized to achieve the highest accuracy in surveying and atmospheric sensing using Global Positioning System (GPS) signals. In this paper we review the theo...

We have developed a tunable temperature profiler based on a highly stable synthe-sizer that can observe at multiple frequencies on the shoulder of the 60 GHz atmospheric oxygen feature. We are developing a similar radiometer to obtain the vertical distribution of water vapor by making observations on the pressure broadened water vapor line from 22...

An advanced microwave radiometer for profiling atmospheric parameters is described in this paper. The method accomplishing profiling is described. The innovations of the radiometer system, including utilization of a stable frequency synthesizer and the calibration system are described. The performance of several mathematical retrieval methods and r...

Multipath and atmospheric effects can limit GPS surveying precision. We surveyed a 43 km baseline using large diameter choke ring antennas to reduce multipath and pointed radiometer and barometric data to correct for atmospheric slant delay. Based on 11 daily solutions, atmospheric slant delay corrections improved vertical precision to 1.2 mm rms a...

We demonstrate sensing of integrated slant-path water vapor (SWV) along ray paths between Global Positioning System (GPS) satellites and receivers. We use double differenc-ing to remove GPS receiver and satellite clock errors and 85-cm diameter choke ring antennas to reduce ground-reflected multi-path. We compare more than 17,000 GPS and pointed ra...

This paper provides an overview of the methodology of and describes preliminary results from an experiment called GPS/MET (Global Positioning System/Meteorology), in which temperature soundings are obtained from a low Earth-orbiting satellite using the radio occultation technique. Launched into a circular orbit of about 750-km altitude and 70° incl...

This paper provides an overview of applications of the Global Positioning System (GPS) for active measurement of the Earth's atmosphere. Microwave radio signals transmitted by GPS satellites are delayed (refracted) by the atmosphere as they propagate to Earth-based GPS receivers or GPS receivers carried on low Earth orbit satellites.The delay in GP...

Atmospheric water vapor was measured with six Global Positioning System (GPS) receivers for 1 month at sites in Colorado, Kansas, and Oklahoma. During the time of the experiment from 7 May to 2 June 1993, the area experienced severe weather. The experiment, called “GPS/STORM,” used GPS signals to sense water vapor and tested the accuracy of the met...

A temperature profiling radiometer based on a highly stable synthesizer, rather than traditionally used Gunn oscillators, has been designed and fabricated under contract to White Sands Missile Range. This profiler is capable of tuning a user-selected ensemble of frequencies in the range of 52.85 to 58.8 GHz as well as fixed water vapor and water ch...

Values of Tmr obtained from current methods and this new approach are compared to those obtained from in situ soundings. Use of forecast model data relieves a WVR site of its dependency on local climatology or the necessity of a nearby sounding, allowing more accurate retrieval of observed conditions and increased flexibility in choosing site locat...

Delay of the Global Positioning System (GPS) signal due to atmospheric water vapor is a major source of error in GPS surveying. Improved vertical accuracy is important for sea level and polar isostasy measurements, geodesy, normal fault motion, subsidence, earthquake studies, air and ground-based gravimetry, ice dynamics, and volcanology. We conduc...

Global Positioning System (GPS) receivers, water vapor radiometers (WVRs), and surface meteorological equipment were operated at both ends of a 50-km baseline in Colorado to measure the precipitable water vapor (PWV) and wet delay in the line-of-sight to GPS satellites. Using high precision orbits, WVR-measured and GPS-inferred PWV differences betw...

Atmospheric water vapor is a source of propagation delay, and therefore error, in Global Positioning System (GPS) geodesy. While GPS geodesy is now capable of millimeter level positioning, unmodelled water vapor can result in errors of several centimeters. Anisotropies in water vapor observed at ground sites have prompted the investigation into the...

Wind and thermodynamic sounding using radar and microwave radiometry is now mature. Typically, radar and radiometric observations are converted into temperature, humidity, cloud liquid profiles and horizontal wind profiles. These profiles can be assimilated into numerical weather models. This approach has the advantage that methods widely used for...

Radiometrics, 2 NCAR, 3 CIRES, 4 Falcon Consultants The US National Weather Service is establishing a Next Generation National Profiler Network (NGNPN) including up to 120 wind and thermodynamic profiler sites. As a part of this process, microwave radiometer profiler, 300-m tower and radiosonde measurements at the NOAA Boulder Atmospheric Observato...