The memo discusses the calibration plan for the GBT 4mm receiver. The specification to maintain b... more The memo discusses the calibration plan for the GBT 4mm receiver. The specification to maintain better than about 3% relative calibration of the instrument drives the calibration strategies and design of the instrument. We plan to adopt a three load calibration system (cold, ambient, and sky). By using the cold and ambient loads we can accurately calibrate the system gains and expect relative calibration uncertainties on the derived T ∗ A antenna temperature scale of order 1–3%. With the addition of the sky-load, we can monitor the weather conditions and verify the self-consitency of the calibration solution with the adopted opacity and astmospheric temperature.
The traditional methods for calibrating single-dish radio telescopes assume that the system gain ... more The traditional methods for calibrating single-dish radio telescopes assume that the system gain is linear: detected power is taken to be proportional to the power incident on the antenna. The assumption is wrong at some low level and noticeably breaks down when observing an object that has a large dynamic range. The high sensitivity, clean beam, and very stable electronics of the Green Bank Telescope (GBT) allow us to detect nonlinearities that would be masked in most other radio telescopes. In particular, the signal processing components of the GBT produce an output power that exhibits at least a quadratic dependence on incident power. Our study indicates that measuring and compensating for the nonlinearity is rather trivial and improves calibration when observing objects with a high dynamic range. Once measured, the nonlinearity is shown to be stable over a typical observing run ( 6-8 hours) with evidence of stability for up to several weeks. We also investigated ways to improve ...
Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valu... more Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.
A sensitive lambda 20cm VLA continuum survey of the Galactic center region, based on multi-config... more A sensitive lambda 20cm VLA continuum survey of the Galactic center region, based on multi-configuration observations, are presented. The high dynamic range images cover the regions within -2o < l < 5o and -40' < b < 40' with spatial resolutions of &ap;30'' and 10''. The wide field imaging technique is used to construct a low-resolution mosaic of 40 overlapping pointings combined with the GBT data filling the missing zero-spacing data. We show high dynamic range images of a number of prominent objects in this region, including Sgr A, B, C, D, and E.
The Robert C. Byrd Green Bank Telescope (GBT) is implementing a new Dynamic Scheduling System (DS... more The Robert C. Byrd Green Bank Telescope (GBT) is implementing a new Dynamic Scheduling System (DSS) designed to maximize the observing efficiency of the telescope while ensuring that none of the flexibility and ease of use of the GBT is harmed and that the data quality of observations is not adversely affected. To accomplish this, the GBT DSS is implementing a dynamic scheduling system which schedules observers, rather than running scripts. The DSS works by breaking each project into one or more sessions which have associated observing criteria such as RA, Dec, and frequency. Potential observers may also enter dates when members of their team will not be available for either on-site or remote observing. The scheduling algorithm uses those data, along with the predicted weather, to determine the most efficient schedule for the GBT. The DSS provides all observers at least 24 hours notice of their upcoming observing. In the uncommon (< 20%) case where the actual weather does not mat...
The Robert C. Byrd Green Bank Telescope's (GBT) Dynamic Scheduling System (DSS), in producti... more The Robert C. Byrd Green Bank Telescope's (GBT) Dynamic Scheduling System (DSS), in production use since September 2009, was designed to maximize observing efficiency while maintaining the GBT's flexibility, improving data quality, and minimizing any undue adversity for the observers. Using observing criteria, observer availability and qualifications, three-dimensional weather forecasts, and telescope state, the DSS software is capable of optimally scheduling observers 24 to 48 hours in advance on a telescope having a wide-range of capabilities in a geographical location with variable weather patterns. Recent improvements for the GBT include an expanded frequency coverage (0.390-90 GHz), proper treatment of fully sampled array receivers, increasingly diverse observing criteria, the ability to account for atmospheric instability from clouds, and new tools for scheduling staff to control and interact with generated schedules and the underlying database.
ASP Conference Series, Vol. XXX, 2008 J. Lewis, R. Argyle, P. Bunclarck, D. Evans, and E. Gonzale... more ASP Conference Series, Vol. XXX, 2008 J. Lewis, R. Argyle, P. Bunclarck, D. Evans, and E. Gonzales-Solares, eds. ... The GBT Dynamic Scheduling System: When do I observe? Guiding Users' Expectations ... Mark Clark1, Dana Balser2, Eric Sessoms3, Carl Bignell1, James ...
The memo discusses the calibration plan for the GBT 4mm receiver. The specification to maintain b... more The memo discusses the calibration plan for the GBT 4mm receiver. The specification to maintain better than about 3% relative calibration of the instrument drives the calibration strategies and design of the instrument. We plan to adopt a three load calibration system (cold, ambient, and sky). By using the cold and ambient loads we can accurately calibrate the system gains and expect relative calibration uncertainties on the derived T ∗ A antenna temperature scale of order 1–3%. With the addition of the sky-load, we can monitor the weather conditions and verify the self-consitency of the calibration solution with the adopted opacity and astmospheric temperature.
The traditional methods for calibrating single-dish radio telescopes assume that the system gain ... more The traditional methods for calibrating single-dish radio telescopes assume that the system gain is linear: detected power is taken to be proportional to the power incident on the antenna. The assumption is wrong at some low level and noticeably breaks down when observing an object that has a large dynamic range. The high sensitivity, clean beam, and very stable electronics of the Green Bank Telescope (GBT) allow us to detect nonlinearities that would be masked in most other radio telescopes. In particular, the signal processing components of the GBT produce an output power that exhibits at least a quadratic dependence on incident power. Our study indicates that measuring and compensating for the nonlinearity is rather trivial and improves calibration when observing objects with a high dynamic range. Once measured, the nonlinearity is shown to be stable over a typical observing run ( 6-8 hours) with evidence of stability for up to several weeks. We also investigated ways to improve ...
Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valu... more Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.
A sensitive lambda 20cm VLA continuum survey of the Galactic center region, based on multi-config... more A sensitive lambda 20cm VLA continuum survey of the Galactic center region, based on multi-configuration observations, are presented. The high dynamic range images cover the regions within -2o < l < 5o and -40' < b < 40' with spatial resolutions of &ap;30'' and 10''. The wide field imaging technique is used to construct a low-resolution mosaic of 40 overlapping pointings combined with the GBT data filling the missing zero-spacing data. We show high dynamic range images of a number of prominent objects in this region, including Sgr A, B, C, D, and E.
The Robert C. Byrd Green Bank Telescope (GBT) is implementing a new Dynamic Scheduling System (DS... more The Robert C. Byrd Green Bank Telescope (GBT) is implementing a new Dynamic Scheduling System (DSS) designed to maximize the observing efficiency of the telescope while ensuring that none of the flexibility and ease of use of the GBT is harmed and that the data quality of observations is not adversely affected. To accomplish this, the GBT DSS is implementing a dynamic scheduling system which schedules observers, rather than running scripts. The DSS works by breaking each project into one or more sessions which have associated observing criteria such as RA, Dec, and frequency. Potential observers may also enter dates when members of their team will not be available for either on-site or remote observing. The scheduling algorithm uses those data, along with the predicted weather, to determine the most efficient schedule for the GBT. The DSS provides all observers at least 24 hours notice of their upcoming observing. In the uncommon (< 20%) case where the actual weather does not mat...
The Robert C. Byrd Green Bank Telescope's (GBT) Dynamic Scheduling System (DSS), in producti... more The Robert C. Byrd Green Bank Telescope's (GBT) Dynamic Scheduling System (DSS), in production use since September 2009, was designed to maximize observing efficiency while maintaining the GBT's flexibility, improving data quality, and minimizing any undue adversity for the observers. Using observing criteria, observer availability and qualifications, three-dimensional weather forecasts, and telescope state, the DSS software is capable of optimally scheduling observers 24 to 48 hours in advance on a telescope having a wide-range of capabilities in a geographical location with variable weather patterns. Recent improvements for the GBT include an expanded frequency coverage (0.390-90 GHz), proper treatment of fully sampled array receivers, increasingly diverse observing criteria, the ability to account for atmospheric instability from clouds, and new tools for scheduling staff to control and interact with generated schedules and the underlying database.
ASP Conference Series, Vol. XXX, 2008 J. Lewis, R. Argyle, P. Bunclarck, D. Evans, and E. Gonzale... more ASP Conference Series, Vol. XXX, 2008 J. Lewis, R. Argyle, P. Bunclarck, D. Evans, and E. Gonzales-Solares, eds. ... The GBT Dynamic Scheduling System: When do I observe? Guiding Users' Expectations ... Mark Clark1, Dana Balser2, Eric Sessoms3, Carl Bignell1, James ...
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