15 research outputs found
Recommended from our members
Validation of the radiation pattern of the VHF MST radar MAARSY by scattering off a sounding rocket's payload
The Middle Atmosphere Alomar Radar System (MAARSY) is a monostatic radar with an active phased array antenna designed for studies of phenomena in the mesosphere and lower thermosphere. Its design, in particular the flexible beam forming and steering capability, makes it a powerful instrument to perform observations with high angular and temporal resolution. For the configuration and analysis of experiments carried out with the radar it is essential to have knowledge of the actual radiation pattern. Therefore, during the time since the radar was put into operation various active and passive experiments have been performed to gain knowledge of the radiation pattern. With these experiments the beam pointing accuracy, the beam width and phase distribution of the antenna array were investigated. Here, the use of a sounding rocket and its payload as a radar target is described which was launched in the proximity of the radar. The analysis of these observations allows the detailed investigation of the two-way radiation pattern for different antenna array sizes and beam pointing positions
Validation of the radiation pattern of the Middle Atmosphere Alomar Radar System (MAARSY)
In 2009/2010 the Leibniz-Institute of Atmospheric Physics (IAP) installed a new powerful VHF radar on the island AndĂžya in Northern Norway (69.30 N, 16.04 E). The Middle Atmosphere Alomar Radar System (MAARSY) allows studies with high spatial and temporal resolution in the troposphere/lower stratosphere and in the mesosphere/lower thermosphere of the Arctic atmosphere. The monostatic radar is operated at 53.5 MHz with an active phased array antenna consisting of 433 Yagi antennas. Each individual antenna is connected to its own transceiver with independent phase control and a scalable power output of up to 2 kW, which implies high flexibility of beam forming and beam steering. During the design phase of MAARSY several model studies have been carried out in order to estimate the radiation pattern for various combinations of beam forming and steering. However, parameters like mutual coupling, active impedance and ground parameters have an impact on the radiation pattern, but can hardly be measured. Hence, experiments need to be designed to verify the model results. For this purpose, the radar has occasionally been used in passive mode, monitoring the noise power received from both distinct cosmic noise sources like e.g. Cassiopeia A and Cygnus A, and the diffuse cosmic background noise. The analysis of the collected dataset enables us to verify beam forming and steering attempts. These results document the current status of the radar during its development and provide valuable information for further improvement
Long-term trends of midlatitude horizontal mesosphere/lower thermosphere winds over four decades
We analyse 43Â years of mesosphere/lower thermosphere (MLT) horizontal winds obtained from a joint analysis of low frequency (LF) spaced receiver lower ionospheric drift measurements from late 1978 through 2008 and VHF meteor radar wind observations since summer 2004 at Collm (51.3ââN, 13.0ââE). Due to limitations of the earlier LF measurements, we restrict ourselves to the analysis of monthly mean winds near 90âkm, which represents the meteor peak height as well as mean LF reflection heights in the MLT. We observe mainly positive trends of the zonal prevailing wind throughout the year, while the meridional winds tend to decrease in magnitude in both summer and winter. Furthermore, there is a change in long-term trends around the late 1990s, which is most clearly visible in summer MLT winds. We compare these measurements with long-term partial reflection radar observations of winds at 81â85âkm over Juliusruh (54.6ââN, 13.4ââE) since 1990, and find general qualitative agreement of trends except for summer. The latter can be explained by the different altitudes considered, and by the latitude dependence of the summer mesospheric jet.</p
Recommended from our members
Mesospheric anomalous diffusion during noctilucent cloud scenarios
The Andenes specular meteor radar shows meteor trail diffusion rates increasing on average by about 10% at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC after exploring possible contributions from thermal tides. To make this claim, the current study evaluates data from three stations at high, middle, and low latitudes for the years 2012 to 2016 to show that NLC influence on the meteor trail diffusion is independent of thermal tides. The observations also show that the meteor trail diffusion enhancement during NLC cover exists only at high latitudes and near the peaks of NLC layers. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that the relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars at high latitudes. © 2019 Author(s)
Validation of the radiation pattern of the Middle Atmosphere Alomar Radar System (MAARSY)
In 2009/2010 the Leibniz-Institute of Atmospheric Physics (IAP) installed a
new powerful VHF radar on the island AndĂžya in Northern Norway
(69.30° N, 16.04° E). The Middle Atmosphere Alomar Radar
System (MAARSY) allows studies with high spatial and temporal resolution in
the troposphere/lower stratosphere and in the mesosphere/lower thermosphere
of the Arctic atmosphere. The monostatic radar is operated at
53.5 MHz with an active phased array antenna consisting of 433 Yagi
antennas. Each individual antenna is connected to its own transceiver with
independent phase control and a scalable power output of up to 2 kW,
which implies high flexibility of beam forming and beam steering. During the
design phase of MAARSY several model studies have been carried out in order
to estimate the radiation pattern for various combinations of beam forming
and steering. However, parameters like mutual coupling, active impedance and
ground parameters have an impact on the radiation pattern, but can hardly be
measured. Hence, experiments need to be designed to verify the model results.
For this purpose, the radar has occasionally been used in passive mode,
monitoring the noise power received from both distinct cosmic noise sources
like e.g. Cassiopeia A and Cygnus A, and the diffuse cosmic background
noise. The analysis of the collected dataset enables us to verify beam
forming and steering attempts. These results document the current status of
the radar during its development and provide valuable information for further
improvement
Recommended from our members
Radar Observation of Extreme Vertical Drafts in the Polar Summer Mesosphere
The polar summer mesosphere is the Earth's coldest region, allowing the formation of mesospheric ice clouds. These ice clouds produce strong polar mesospheric summer echoes (PMSE) that are used as tracers of mesospheric dynamics. Here, we report the first observations of extreme vertical drafts (+/-50 ms [hoch]-1) in the mesosphere obtained from PMSE, characterized by velocities more than five standard deviations larger than the observed vertical wind variability. Using aperture synthesis radar imaging, the observed PMSE morphology resembles a solitary wave in a varicose mode, narrow along propagation (3â4 km) and elongated (>10 km) transverse to propagation direction, with a relatively large vertical extent (~13 km). These spatial features are similar to previously observed mesospheric bores, but we observe only one crest with much larger vertical extent and higher vertical velocities
Mesospheric anomalous diffusion during noctilucent cloud scenarios
The Andenes specular meteor radar shows meteor trail diffusion rates increasing on average by
about 10 % at times and locations where a lidar observes noctilucent
clouds (NLCs). This high-latitude effect has been attributed to the presence
of charged NLC after exploring possible contributions from thermal tides. To
make this claim, the current study evaluates data from three stations at
high, middle, and low latitudes for the years 2012 to 2016 to show that NLC
influence on the meteor trail diffusion is independent of thermal tides. The
observations also show that the meteor trail diffusion enhancement during NLC
cover exists only at high latitudes and near the peaks of NLC layers. This
paper discusses a number of possible explanations for changes in the regions
with NLCs and leans towards the hypothesis that the relative abundance of
background electron density plays the leading role. A more accurate model of
the meteor trail diffusion around NLC particles would help researchers
determine mesospheric temperature and neutral density profiles from meteor
radars at high latitudes.</p
VHF antenna pattern characterization by the observation of meteor head echoes
The Middle Atmosphere Alomar Radar System (MAARSY) with its active
phased array antenna is designed and used for studies of phenomena in the
mesosphere and lower atmosphere. The flexible beam forming and steering
combined with a large aperture array allows for observations with a high temporal
and angular resolution. For both the analysis of the radar data and the
configuration of experiments, the actual radiation pattern needs to be known.
For that purpose, various simulations as well as passive and active
experiments have been conducted. Here, results of meteor head echo
observations are presented, which allow us to derive detailed information of
the actual radiation pattern for different beam-pointing positions and the
current health status of the entire radar. For MAARSY, the described method
offers robust beam pointing and width estimations for a minimum of a few days
of observations
Multi beam observations of cosmic radio noise using a VHF radar with beam forming by a Butler matrix
The Leibniz-Institute of Atmospheric Physics (IAP) in KĂŒhlungsborn started
to install a new MST radar on the North-Norwegian island AndĂžya
(69.30° N, 16.04° E) in 2009. The new Middle Atmosphere Alomar
Radar System (MAARSY) replaces the previous ALWIN radar which has been
successfully operated for more than 10 years. The MAARSY radar provides
increased temporal and spatial resolution combined with a flexible sequential
point-to-point steering of the radar beam. To increase the spatiotemporal
resolution of the observations a 16-port Butler matrix has been built and
implemented to the radar. In conjunction with 64 Yagi antennas of the former
ALWIN antenna array the Butler matrix simultaneously provides 16 individual
beams. The beam forming capability of the Butler matrix arrangement has been
verified observing the galactic cosmic radio noise of the supernova remnant
Cassiopeia A. Furthermore, this multi beam configuration has been used in
passive experiments to estimate the cosmic noise absorption at 53.5 MHz
during events of enhanced solar and geomagnetic activity as indicators for
enhanced ionization at altitudes below 90 km. These observations are
well correlated with simultaneous observations of corresponding beams of the
co-located imaging riometer AIRIS (69.14° N, 16.02° E) at
38.2 MHz. In addition, enhanced cosmic noise absorption goes along with
enhanced electron densities at altitudes below about 90 km as observed
with the co-located Saura MF radar using differential absorption and
differential phase measurements
Validation of the radiation pattern of the VHF MST radar MAARSY by scattering off a sounding rocket's payload
The Middle Atmosphere Alomar Radar System (MAARSY) is a monostatic radar with
an active phased array antenna designed for studies of phenomena in the
mesosphere and lower thermosphere. Its design, in particular the flexible
beam forming and steering capability, makes it a powerful instrument to
perform observations with high angular and temporal resolution. For the
configuration and analysis of experiments carried out with the radar it is
essential to have knowledge of the actual radiation pattern. Therefore,
during the time since the radar was put into operation various active and
passive experiments have been performed to gain knowledge of the radiation
pattern. With these experiments the beam pointing accuracy, the beam width
and phase distribution of the antenna array were investigated. Here, the use
of a sounding rocket and its payload as a radar target is described which was
launched in the proximity of the radar. The analysis of these observations
allows the detailed investigation of the two-way radiation pattern for
different antenna array sizes and beam pointing positions