George Seielstad

• Doctor of Philosophy
• Professor at University of Montana

We present VLBI and VLA maps of the superluminal radio source 3C 120 (z = 0.03). The 18 cm VLBI maps shown in Figures 1 and 2c were constructed from a 14 station VLBI observation on 10, 11 October 1982. The map in Figure 1 is at full spatial resolution. The Figure 2c map was made from a uv-tapered data set and shows the extended emission. The VLBI...

Superluminal motions were first seen in 3C 120 between 1972.5 and 1974.4 (Seielstad et al . 1979 and references therein). Between 1975 and 1980, the source was monitored along with 3C 273 and 3C 345 by the Caltech group. One reasonably clear episode of expansion was seen in 1979 (Walker et al . 1982) but, for most of the time, the source evolution...

Faculty, students, and staff from eight universities in the U.S. Northern Great Plains formed the Upper Midwest Aerospace Consortium (UMAC ) to lead a regional transition to sustainability . One major focus was on agriculture, an important part of the region’s economy and social structure. By forming a learning community in concert with farmers and...

The US Northern Great Plains is one of the world’s most agriculturally productive areas. Growers in the region are eager to adopt modern technology to improve productivity and income. Use of information derived from remote sensing satellites to better manage farms and rangelands while reducing environmental impacts has gained popularity in recent y...

A web-based decision support tool, zone mapping application for precision farming (ZoneMAP, http://zonemap.umac.org), has been developed to automatically determine the optimal number of management zones and delineate them using satellite imagery and field data provided by users. Application rates, such as of fertilizer, can be prescribed for each z...

Using remote sensing to characterize the hydrologic behavior of the land surface on a routine basis is of considerable practical interest. Technique combining information on land and atmospheric properties with remotely observed variables has improved prediction of a number of hydrological variables, such as evapotranspiration rate, which is an imp...

“Our Changing Planet” is a series of 90‐second television episodes whose purpose is to enhance public understanding of the global environment and the changes it is undergoing. The hope is that with this deeper understanding, people will appreciate the need to modify behaviors that produce negative environmental effects. The episodes are produced by...

Water and nitrogen stress impact hard red spring wheat (Triticum aestivum) crop reflectance, yield and grain quality. To minimize yield losses from nitrogen (N) and water stress, it is essential to apply appropriate N in relation to water stress. The objective of this experiment was to determine the influence of N and water stress on hard red sprin...

Achieving sustainability, i.e., meeting the needs and values of the present generation without compromising the ability of future generations to meet theirs, is the biggest challenge facing humanity in the 21st century. While solid science is necessary, it is not by itself sufficient to introduce the changes in lifestyles and business practices tha...

Oil spills in the ocean are one of major environmental concerns, especially in the coastal waters. Multispectral satellite sensors, such as AVHRR, MODIS and MERIS, have been used to detect oil spills which often exhibit a differing spectral reflectance than the surrounding waters. Some simple image processing methods, such as contrast enhancement,...

Satellite imagery has proven potential in farm level applications, especially in the US Upper Midwest where the farm sizes are large enough to be studied using high and medium resolutions. In order for farmers to use this technology to improve their productivity and income, it is imperative that they be sufficiently exposed to the technology so tha...

We are living in a definite time of change. Distinct changes are being experienced in our most sacred and natural environments. This is especially true on Native lands. Native people have lived for millennia in distinct and unique ways. The knowledge of balancing the needs of people with the needs of our natural environments is paramount in all tri...

Sustainability, meaning meeting human needs and values while also preserving Earth's life-support systems, can only be achieved if a just and equitable distribution of access to natural resources exists. The same environment is shared by all peoples; all must have an interest in preserving it; therefore all must receive a fair share of the benefits...

The University of North Dakota (UND) is developing the agricultural camera (AgCam) payload to capture precision agriculture imagery from an Earth-observing window onboard the International Space Station (ISS). Before AgCam operations can begin, however, the AgCam system must be thoroughly tested in order to prove its safety, reliability, and compat...

The agricultural camera (AgCam) is a two-band digital imaging payload that will be operated in the pressurized Window Observational Research Facility (WORF) onboard the International Space Station. Its primary mission is to provide on-demand, high-resolution remote sensing imagery to support precision agriculture and natural resource end-users in t...

Institutions participating in the Upper Midwest Aerospace Consortium (UMAC) are the Universities of North Dakota, Montana, Idaho, and Wyoming; North Dakota, South Dakota, and Montana State Universities; the South Dakota School of Mines and Technology; and Sinte Gleska University. UMAC?s purpose is to build learning communities integrating researche...

Farmers throughout the world are constantly searching for ways to maximize their returns. Remote Sensing, Geographic Information Systems (GIS), and Global Positioning Systems (GPS) may provide technologies needed for farmers to maximize the economic and environmental benefits of precision farming. However, most farmers do not have the skills to uti...

The initial attitude estimation of the airborne navigation system greatly affects the overall attitude accuracy. The initial alignment depends on the inertial measurement unit's performance. In the case of the tactical grade inertial measurement unit, even though tilt angles can be estimated relatively accurate by using accelerometer outputs, it is...

The Upper Midwest Aerospace Consortium has developed a crop and range alert system to provide farmers, ranchers, land managers from the Native American Community, government agencies and non-governmental organizations with frequent and near real time remote sensing data to enable decisions that both maximize the producer's income and protect the en...

The Upper Midwest Aerospace Consortium, an organization of remote sensing research groups at eight Upper Midwest universities with its headquarters located at the University of North Dakota (UND), has entered into a strategic alliance with the UND School of Engineering & Mines to design Earth imaging sensors. The first of these instruments, the Air...

The Upper Midwest Aerospace Consortium, an organization of remote sensing research groups at eight Upper Midwest universities with its headquarters located at the University of North Dakota (UND), has entered into a strategic alliance with the UND School of Engineering & Mines to design Earth imaging sensors. The first of these instruments, the Air...

In the U.S. Northern Great Plains, growing seasons are short but extremely productive. Farms and ranches are large, so many of precision agriculture's early adopters reside in the region. Crop yield maps at season's end reveal sizable variations across fields. Farm management relying upon uniform chemical applications is ineffective and wasteful. W...

A multidisciplinary team of students and faculty from Mechanical and Electrical Engineering and the John D. Odegard School of Aerospace Sciences at the University of North Dakota (UND), along with an industrial partner, DIGIT, Inc., has developed and built a remote sensing camera array. The Airborne Environmental Research Observational Camera (AERO...

Because agricultural production in the northern Great Plains contributes significantly to both domestic and international markets the impacts of climate change, as well as the response strategies undertaken by the region's residents, will be felt throughout the nation and the world. The national assessment of Climate Change Impacts on the United St...

Building learning communities to engage the public in identifying and solving local and regional environmental problems is the vision of the newly created Northern Great Plains Center for People and the Environment at the University of North Dakota. The Center serves as an Environmental Information Bridge between science and society for citizens of...

In the Northern Great Plains of the United States, growing seasons are short (80-120 days) but extremely productive. Farms and ranches are large (>1000 acres), so many of precision agriculture's early adopters reside in the region. Management optimization depends on decisions taken based on past as well as in-season information. Spatial data is an...

The NRAO seven-beam receiver was used on the 43 m telescope in Green Bank, WV during 1990 January and March to make 4.85 GHz continuum maps covering the area -40 degrees < delta < 5 degrees, 0 hours < alpha < 20 hours. The data were reduced with AIPS to yield total-intensity maps covering Omega = 3.8 sr with theta = 7 arcmin FWHM resolution.

We discuss gigabit network applications enabled by “Mission to Planet Earth”, an international effort to monitor the Earth as a system. We describe the design of a network architecture to support applications developed as part of this program; introduce a new component, public access resource centers (PARCs); and discuss how PARCs would facilitate...

The National Radio Astronomy Observatory (NRAO) seven-beam receiver was used on the 91 m telescope in Green Bank, WV during 1986 November to survey the declination band 0 deg less than delta less than +75 deg at 4.85 GHz. We made sky maps from the 1986 data alone, primarily for comparison with the epoch 1987 maps (Condon et al., (1989)) to allow va...

The NRAO seven-beam receiver was used on the 43 m telescope in Green Bank, WV during 1990 January and March to make a 4.85 GHz continuum sky survey of the area -40°<δ< +5°, 0h<α20h. The data were reduced with AIPS to yield total-intensity maps covering Ω∼3.8 sr with θ∼7 arcmin FWHM resolution (∼2×105 beams sr-1). The rms map noise plus confusion is...

A 4.85-GHz continuum sky survey of the area delta = -40 to +5 deg and alpha = 0-20 h made during January-March 1990 is presented. The data were reduced with AIPS to yield total-intensity maps covering Omega of about 3.8 sr with theta of about 7 arcmin FWHM resolution (about 2 exp 5 beams/sr); the rms map noise plus confusion is about 3 mJy/beam. Th...

The new seven beam receiver and lateral-focus corrector were used on the NRAO 91 m telescope during October 1987 to make a total-power survey of the declination band delta between 0 and + 75 deg at 4.85 GHz. The data were reduced with AIPS to yield sky maps covering 6.0 sr with 3.7 arcmin x 3.3 arcmin resolution. The rms map noise is 5 mJy, about f...

In this paper, 10.7 GHz observations of 55 Seyfert galaxies, mostly from Markarian lists are presented. Ten galaxies were detected with certainty, and probably five more. The results are briefly discussed. Inasmuch as the limited sample allows, it is concluded that the detection statistics are similar for both Seyfert 1 and Seyfert 2 galaxies. Seyf...

The large radio galaxy NGC 6251 has been observed with an 11-telescope VLBI array, including the full VLA, at 18 cm. High-dynamic-range maps of both the VLBI-scale and VLA-scale radio structure from these observations, as well as hybrid maps from earlier VLBI experiments at 6 and 13 cm, are presented. The 18-cm VLBI hybrid map has an unusually high...

Papers are presented on life in space and humanity on earth, the Ozma project, the evolution of strategy for SETI, the search for biomolecules in space, a symbiotic SETI search, searches in the optical portion of the spectrum, a search for SETI targets, and a Milky Way search strategy for extraterrestrial intelligence. Topics discussed include SETI...

The compact ratio structure of the quasar 3C 273 has been monitored with a VLBI array at 5.0 and 10.7 GHz at six-month intervals during 1977-1982. THe VLBI monitoring observations, data reduction, calibration, and mapping techniques are described, and hybrid maps from the monitoring program are presented along with a brief discussion of the main fe...

Results from new VLBI observations of 3C 120 in the period 1980.5 to 1982.5 are reported. The new maps show a much more complex structure than previously realized. Rapid evolution of the components is evident.

The authors present VLBI and VLA maps of the superluminal radio source 3C 120 (z = 0.03). The VLBI maps show a jet ≡175 pc long with distinct knots and bends.

Superluminal motions were first seen in 3C 120 between 1972.5 and 1974.4 (Seielstad et al. 1979 and references therein). Between 1975 and 1980, the source was monitored along with 3C 273 and 3C 345 by the Caltech group. One reasonably clear episode of expansion was seen in 1979 (Walker et al. 1982) but, for most of the time, the source evolution wa...

The authors have measured the 10.8-GHz flux densities of 285 radio sources at 14 epochs between January 1979 and November 1982. For the subset of 258 objects constituting a complex flux-density-limited sample selected at 5 GHz, it is found that at least 45% vary within ten years. About nine-tenths of the steep spectrum (α ≤ -0.5) sources do not var...

Observations of the compact radio structure of the quasar 3C 345 have been made at eight epochs between 1979 and 1981, using a very long baseline interferometer comprising five telescopes. The sequence of hybrid maps, alternating between 5.0 and 10.7 GHz, shows a bright unresolved "core" and a curved jet at each epoch. Two "knots" in the jet separa...

A position angle coincidence in 3C 345 between the elongation seen in 1971-1975 at 1-1.5 milli-arcsec from the core, and the outer component seen in 1978-1981 at 3.5-5 milli-arcsec, is found to provide evidence for rectilinear motion. The inner component seen in 1978-1981 at 1-2 milli-arcsec is determined to be at a different position angle. Result...

In recent years the angular distribution of intensity of the compact cores of quasars and radio galaxies has been mapped in detail by very long baseline interferometry (VLBI) arrays1,2. These observations have shown that asymmetric radio structure is common in active nuclei3, and that a high proportion of the brightest sources exhibit superluminal...

A survey at 10.7 GHz covering 0.00158 sr of sky to a flux density limit of 50 mJy and a completeness level of three-fourths is discussed. The survey samples five 1-deg x 1-deg squares at a grid interval of 2 arcmin in each coordinate; two of the regions are also surveyed by the Einstein Observatory at X-ray wavelengths, a third lies within a Parkes...

Observations of the solar limb at 2.6mm have been obtained which provide a 6-arcsec FWHM resolution one-dimensional synthesized beam that suffices for the resolution of the spicule forest's contribution, when it is seen edge-on at the solar limb. The data are analyzed by (1) direct interpretation of the simple dependence of observed amplitudes and...

Results of VLBI observations of the milliarcsecond scale structure of the radio galaxy 3C 120 at wavelengths of 2.8 and 6.0 cm are reported for seven epochs between 1978.24 and 1980.27. The structure is highly variable, typically consisting of several features distributed along position angle -108 deg + or - 10 deg. The easternmost feature is relat...

Figure 1 shows hybrid maps of the core of 3C 273B at five epochs, made with arrays of 4 or 5 VLBI antennas. The maps span a period of 3.5 years. They all show a bright eastern peak and a lower-brightness extension to the west. There is a local maximum in the western extension between 6 and 8 milliarcsec from the main peak. This “blob” moves steadil...

Figure 1 shows hybrid maps of the core of 3C 273B at five epochs, made with arrays of 4 or 5 VLBI antennas. The maps span a period of 3.5 years. They all show a bright eastern peak and a lower-brightness extension to the west. There is a local maximum in the western extension between 6 and 8 milliarcsec from the main peak. This “blob” moves steadil...

Figure 1 shows hybrid maps of the core of 3C 273B at five epochs, made with arrays of 4 or 5 VLBI antennas. The maps span a period of 3.5 years. They all show a bright eastern peak and a lower-brightness extension to the west. There is a local maximum in the western extension between 6 and 8 milliarcsec from the main peak. This “blob” moves steadil...

The quasar 3C 345 has been studied at eight epochs between 1977.56 and 1979.92 using very-long-baseline interferometry, alternating between frequencies of 10.65 and 5.01 GHz. Hybrid maps for each epoch show that the source comprises a bright, barely-resolved 'core' with an inverted spectrum, and an elongated region of emission extending approximate...

Maps of the radio structure of the quasar 3C273 provide evidence of a superluminal expansion during the period 1977-1980. The superluminal expansion might be attributed to the movement of a single knot away from the nucleus along the jet. The apparent constant velocity of 10 times the speed of light is an important constraint on theories of apparen...

We have determined the distribution of defections due to sky temperature fluctuations at 10.6 GHz. If all the defections are due to fine structure in the cosmic microwave background, we limit these fluctuations to ΔT/T ≲ 2.5 × 10-4 on an angular scale of 11 arcmin. If, on the other hand, all the deflections are due to confusion among discrete radio...

Very long baseline interferometer observations at 4997 MHz (λ = 6 cm) on European and intercontinental baselines with lengths up to 1.35 108λ have been used to probe the milliarc s structure of the BL Lacertae objects AO 0235+164, 0735+178, BL Lac, 1749+701, Mk 421, and 3C 66A. Two sets of observations are reported, made in November 1978 and March...

SS 433 was detected and partially resolved at 2290 MHz on baselines with fringe spacings of 1.4, 0.1, and 0.003 arcsec. It was also detected at 8420 MHz on a baseline with a fringe spacing of 0.009 arcsec. Simple models of the source, consistent with the limited data, have elongated structures greater than 0.1 arcsec in size with position angles in...

The superluminal behavior of 3C 120, 3C 273, and 3C 345 has been reexamined in light of new hybrid maps of these objects. The maps of 3C 273 and 3C 345 are consistent with superluminal expansion. 3C 120 appeared to expand superluminally from 1972.6 to 1974.5, but the evidence has been inconclusive since 1974.5. It is suggested that the jetlike stru...

view of the nuclei of galaxies and of quasars, an understanding of which appears essential to a thorough interpretation of galactic structure. VLSI experiments have progressed rapidly from the initial two-station runs to routine, frequent operations of three, four, and five stations, with six- and seven-element arrays being utilized occasionally. I...

Results are reported for VLBI measurements of the compact extragalactic radio sources 3C 120, 3C 273, 3C 279, and 3C 345, which were performed at six epochs between 1975.40 and 1977.13 at a frequency of 10,650 MHz as well as in 1976.52 and 1977.41 at a frequency of 5010 MHz. The observations were made to study possible changes in source structure....

A survey at 8085 MHz of 0.181 sr of sky having absolute values of galactic latitude greater than 10 deg and absolute values of declination greater than or equal to 1.5 deg has revealed 64 sources, 35 of which constitute a sample 85% complete to an 8085-MHz flux-density upper limit of 0.40 Jy. More than two-thirds of the sources can be optically ide...

The mean and the median linear polarization at wavelengths of 3.7, 6, 11, 31, and 49 cm are calculated for various types of quasars characterized by the presence or absence of optical absorption lines. No differences in mean linear polarization as large as two standard deviations are observed between absorption and nonabsorption quasars, but it is...

Observed variations concerning the brightness distributions in four extragalactic radio sources were so rapid that the apparent transverse velocity of expansion is greater than the velocity of light. The term superluminal is used to describe this phenomenon. A review is provided of the observations of superluminal expansions. Attention is given to...

The brightness distribution of the quasar 3C 345 at lambda=2.8 cm is accurately modeled with two Gaussian elliptical components. Observations at four epochs between 1974.15 and 1975.68 show that the separation of the components increased from 1.23 to about 1.61 milli-arcsec, at a rate 0.2 milli-arcsec per year. The apparent transverse velocity is v...

We have monitored the integrated 5-GHz radio emission, including the complete polarization state as well as the flux density, of 15 compact radio sources for a period of 27 months. In the data presented herein there are several examples of interesting time variations. However, the diverse behavior and other properties of the sources defy any satisf...

Observations of flux density and very-long-baseline interferometric measurements of the rapidly variable radio source 3C 120 are shown to support a model first proposed by Ozernoy and Sazonov. This model suggests that explosions of supernova magnitude occur approximately every 1.2 years at the center of the galaxy, ejecting two similar synchrotron-...

Aperture synthesis observations with an angular resolution ~2 of two late-type galaxies have revealed H I distributions some 1.5 times larger than their photographic images. IC 2574, classified as an irregular galaxy, has a well-organized velocity field typical of a late spiral galaxy. The major H I conceritratioris do not correspond to the bri...

The total intensity and linearly polarized emission from the Crab Nebula (Taurus A) were synthesized to a resolution of approximately 1 arc-minute at both 1420 and 2880 MHz. From these data were calculated the spectral index, rotation measure, intrinsic position angle, and depolarization ratio distributions. Then, combined with a source model, the...

During its occultation by the sun in October 1969, the position of the radio source 3C279 was interferometrically monitored to determine the deviation of its 9.602-GHz radiation in the solar gravitational field. Rapid instrumental calibration and negligible coronal diffraction enabled the measurement of a general relativity deflection of 1.77′′±0.2...

The Upper Midwest Aerospace Consortium (UMAC) has changed agricultural practices in the following ways: (1) farmers and ranchers have become partners with, not clients of, researchers; (2) experiments are carried out in the field rather than on small experimental plots; (3) the field is considered an agro-ecosystem, with all the complexities of mul...