A wing pod-based millimeter wavelength airborne cloud radar

Vivekanandan, Jothiram; Ellis, Scott; Tsai, Pei-Sang; Loew, Eric; Lee, W.-C.; Emmett, Jonathan; Dixon, Michael; Burghart, C.; Rauenbuehler, S.

doi:10.5194/gi-4-161-2015

Cited by 27 publications

(21 citation statements)

References 36 publications

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“…Using three range bins in this way prevents small point targets, such as birds, from being mistakenly identified as the surface. The HCR was run with a 40-m pulse length that was oversampled by a factor of 2 to 20-m range gates [complete system characteristics can be found in Vivekanandan et al (2015)]. The result is that the surface echo typically occupies several range bins.…”

Section: Surface-reference Vr Correction Challenges and Methodsmentioning

confidence: 99%

“…The correction proposed here was developed with, and applied to, nadir-pointing data from the National Center for Atmospheric Research (NCAR) HIAPER Cloud Radar (HCR; Vivekanandan et al 2015). HCR is a W-band, dual-polarization, Doppler airborne research radar that flies in an underwing pod on the NSF/NCAR Gulfstream-V High-Performance Instrumented Airborne Platform for Environmental Research (GV HIAPER) aircraft (UCAR/NCAR 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The pointing angle is updated at 20 Hz, thus keeping the beam pointed very close to the desired direction. At vertical incident, this strategy mitigates the errors from the unknown horizontal wind that are projected into a nonvertical pointing beam, which can be substantial for relatively small offsets (Vivekanandan et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Use of the Earth’s Surface as a Reference to Correct Airborne Nadir-Looking Radar Radial Velocity Measurements for Platform Motion

Ellis

Tsai

Burghart

et al. 2019

Journal of Atmospheric and Oceanic Technology

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A technique for correcting radar radial velocity Vr in airborne, nadir-pointing radar data using the surface of Earth as a reference is proposed and tested. Operating airborne Doppler radars requires correcting the radial velocity for platform motion. This can be accomplished with accurate beam-pointing and platform motion measurements. However, there are often residual pointing errors due to drift in inertial navigation systems (INS) and/or errors in platform-relative pointing. The technique proposed here takes advantage of the fact that the surface is stationary and the mean of the measured Vr at the surface [Formula: see text] should be 0 m s−1. Therefore, if a good estimate of the mean [Formula: see text] is made, it can be subtracted from the measured Vr to correct for errors due to residual pointing errors. The [Formula: see text] data contain many independent deviations from 0 m s−1 due to various causes, including measurement variance and large deviations due to surface features. These deviations must be filtered out of [Formula: see text] before the surface reference can be applied to correct the Vr data. A two-step filtering process was developed and tested. The first step removes large deviations in [Formula: see text] and the second step removes the measurement noise. The technique was examined using data from three field campaigns and was found to improve the quality of Vr in all cases. The Vr bias was removed and the variance was substantially reduced. The approach is generally applicable to nadir-pointing airborne radar data.

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Section: Surface-reference Vr Correction Challenges and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Use of the Earth’s Surface as a Reference to Correct Airborne Nadir-Looking Radar Radial Velocity Measurements for Platform Motion

Ellis

Tsai

Burghart

et al. 2019

Journal of Atmospheric and Oceanic Technology

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“…One of the instruments that is deployed on the aircraft is the HIAPER Cloud Radar (HCR, Vivekanandan et al, 2015), a Wband, dual-polarization, Doppler radar which is mounted in an underwing pod. A single len s antenna is used for both transmit and receive.…”

Section: Introductionmentioning

confidence: 99%

The NCAR airborne 94-GHz cloud radar: calibration and data processing

Romatschke¹,

Dixon²,

Tsai³

et al. 2022

Preprint

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The 94-GHz airborne HIAPER Cloud Radar (HCR) has now been deployed in three major field campaigns. NCAR has developed an extensive set of quality assurance and quality control procedures which are applied to all collected data.Engineering measurements performed both in the laboratory and in an antenna measurement chamber yielded calibration characteristics for the antenna, reflector, and radome. These calibration results are applied during flight, to produce the radar moments available in real-time. However, temperature changes in the instrument during flight affect the receiver gains, leading to some bias in the calibration values applied in real time. Post project, we estimate the temperature -induced gain errors and apply gain corrections to improve the quality of the final data set. In addition, the reflectivity calibration is monitored by comparing sea surface cross section measurements against theoretically -calculated model values. These comparisons confirm that HCR is calibrated to within 1 dB of the theory. A radar echo classification algorithm was developed to identify "cloud echo" and distinguish it from artifacts such as the echo from the surface, transmitter leakage , and a number of other categories.Model reanalysis data and digital terrain eleva tion data were interpolated to the radar time-range grid of the radar data, to provide an environmental reference. These fields were used for the sea surface calibration and also are made available as an aid for scientific research.

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“…Dual-polarized Cassegrain antennas at W-band have found extensive applications in millimeter cloud radar [1][2][3]. Millimeter cloud radar with dual-polarization capability is highly desirable for the current estimation of microphysical properties of cloud [4]. As we know, the polarization of the linear polarized incident wave will be rotated by the non-spherical cloud particle such as water-drop or ice, and in this case a dual-polarized Cassegrain antenna is deployed to receive the vertical and horizontal polarization components in the backscattering wave respectively.…”

Section: Introductionmentioning

confidence: 99%

A Novel W-Band Dual-Polarized Cassegrain Antenna for Cloud Radar

Yu¹,

Xia²,

Chen³

et al. 2016

PIER Letters

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A W-band dual-polarized Cassegrain antenna for cloud radar is proposed. The aperture diameter of the main reflector of the antenna is 50 cm. By using a modified Magic-T structure in the feed horn, the antenna is dual-polarized with high port isolation. The measured results show that the port isolation is 44.7 dB. The gains are 47.3 dB and 49.5 dB for the two ports at 94 GHz, respectively, and the efficiency of the antenna is better than 87%.

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A wing pod-based millimeter wavelength airborne cloud radar

Cited by 27 publications

References 36 publications

Use of the Earth’s Surface as a Reference to Correct Airborne Nadir-Looking Radar Radial Velocity Measurements for Platform Motion

Use of the Earth’s Surface as a Reference to Correct Airborne Nadir-Looking Radar Radial Velocity Measurements for Platform Motion

The NCAR airborne 94-GHz cloud radar: calibration and data processing

A Novel W-Band Dual-Polarized Cassegrain Antenna for Cloud Radar

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