The GLO instrument concept is a VNIR/MWIR solar occultation sensor designed to measure (all at < 1 km vertical resolution) O3, H2O, CH4, CO, HF, HCN, HCl, HDO, N2O, CO2 (for temperature), and aerosol from orbital altitudes. The vertical measurement range spans the entire middle atmosphere, but the sensor has been designed to particularly target transport and composition in the UTLS. With its small form factor and modest spacecraft requirements, GLO is well suited for constellation applications. We will describe one such implementation of GLO. The instrument concept, measurement and data acquisition approach, and potential applications will be discussed.
We report on the design and demonstration of a CubeSat-scale spatial heterodyne spectrometer suitable for high-resolution imaging of molecular bands against the earth surface or limb. The demonstration instrument is tuned to a methane absorption band at 1637-1657 nm. The spectral resolution of 0.13 nm is sufficient to resolve individual methane lines, intervening CO2 absorption, and background scattering. The all-transmissive design utilizes volume holographic gratings for high optical efficiency.
High-framerate imaging enables the long-range characterization of the vibration modes and amplitudes of a passively
illuminated structure. The vibration signature arises from modulation of the bidirectional reflection distribution function
(BRDF) as the surface normal oscillates with respect to a fixed, directional source. In this paper we consider the
instrument design characteristics and environmental factors that limit passive vibrometer performance including BRDF
angle sensitivity, receiver spatial resolution, interference from atmospheric scintillation, and intrinsic detector
performance. We here identify a sensor architecture that is capable of characterizing surface vibration at amplitudes
below 1 mrad root mean square (RMS) and discuss detector technology that can further improve long-range vibrometer
sensitivity.
KEYWORDS: Quantum cascade lasers, Black bodies, Copper, Temperature metrology, Sensors, Signal detection, Mid-IR, Infrared radiation, Environmental sensing, Surgery
Continuous improvements of quantum cascade laser (QCL) technology have extended the applications in environmental
trace gas monitoring, mid-infrared spectroscopy in medicine and life science, law enforcement and homeland security
and satellite sensor systems. We present the QCL based emissivity monitor for the CORSAIR blackbody. The emissivity
of the blackbody was designed to be better than 0.9999 for the spectral range between 5 to 50μm. To actively monitor
changes in blackbody emissivity we employ a QCL-based infrared illumination source. The illumination source
consisted of a QCL and thermoelectric cooler (TEC) unit mounted on a copper fixture. The stability of the QCL was
measured for 30, 60, and 90s operation time at 1.5A driving current. The temperature distribution along the laser
mounting fixture and time dependent system heat dispersion were analyzed. The results were compared to radiative and
conductive heat transfer models to define the potential laser operating time and required waiting time to return to initial
temperature of the laser mount. The observed cooling behaviour is consistent with a primarily conductive heat transfer
mechanism.
The ValidWind™ system employs an XL200 laser rangefinder to track small, lightweight, helium-filled balloons
(0.33 meters, 0.015 kg). We record their trajectories (range resolution 0.5 meters) and automatically produce local
wind profiles in real time. Tracking range is enhanced beyond 2 km by applying retro-reflector tape to the balloons.
Aerodynamic analysis shows that ValidWind balloon motion is well coupled to the local wind within relaxation
times ~ 1 second, due to drag forces at subcritical Reynolds numbers Re < 2×105. Such balloons are Lagrangian
sensors; i.e., they move with the wind as opposed to being fixed in space. In a field campaign involving many
balloons, slight variations in ground level winds at launch lead to trajectory patterns that we analyze to derive 3D
maps of the vertical and horizontal wind profiles downwind of the launch area. Field campaigns are focused on
likely sites for wind power generation and on facilities from which airborne particulates are emitted. We describe
results of wind measurements in Utah near the cities of Clarkston, Logan, and Ogden. ValidWind is a relatively
inexpensive wind sensor that is easily and rapidly transported and deployed at remote sites. It is an ideal instrument
for wind prospecting to support early decisions required, for example, in siting meteorology towers. ValidWind
provides high-resolution, real time characterization of the average and changing 3D wind fields in which wind
power turbines and other remote sensors must operate.
The signal from a laser range finder is greatly enhanced by attaching a retroreflector to the target. Low-cost, lightweight retroreflectors can be fabricated from conspicuity tape. This work reports the near-infrared retroreflection characteristics of conspicuity tape from bidirectional reflectance distribution function (BRDF) measurements at 904 nm. BRDF values approach 500 sr-1 at near normal incidence. The BRDF test results are applied to predict the performance of alternate lightweight retroreflector designs suitable for tracking small helium balloons. The combination of a range finder and retroreflecting balloon enable a low-cost, high-performance method for wind profiling.
VisibleWindTM is developing an inexpensive rapid response system, for accurately characterizing wind shear and
small scale wind phenomena in the boundary layer and for prospecting suitable locations for wind power turbines.
The ValidWind system can also collect reliable "ground truth" for other remote wind sensors. The system employs
small (0.25 m dia.) lightweight balloons and a tracker consisting of an Impulse 200 XL laser rangefinder coupled to
a PC for automated data recording. Experiments on balloon trajectories demonstrate that the laser detection of range
(± 0.5 m), together with measured azimuth and altitude, is an inexpensive, convenient, and capable alternative to
other wind tracking methods. The maximum detection range has been increased to 2200 meters using micro-corner-cube
retroreflector tape on balloons. Low power LEDs enable nighttime tracking. To avoid large balloon gyrations
about the mean trajectory, we use balloons having low ascent rates and subcritical Reynolds numbers. Trajectory
points are typically recorded every 4 - 7 seconds. Atmospheric features observed under conditions of inversions or
"light and variable winds" include abrupt onsets of shear at altitudes of 100-250 m, velocity changes of order 1-3
m/s within layers of 10-20 m thickness, and veering of the wind direction by 180 degrees or more as altitude
increases from 300 to 500 m. We have previously reported comparisons of balloon-based wind profiles with the
output of a co-located sodar. Even with the Impulse rangefinder, our system still requires a "man in the loop" to
track the balloon. A future system enhancement will automate balloon tracking, so that laser returns are obtained
automatically at 1 Hz. While balloon measurements of large-scale, high altitude wind profiles are well known, this
novel measurement system provides high-resolution, real-time characterization of the fluctuating local wind fields at
the bottom of the boundary layer where wind power turbines and other remote wind sensors must operate.
The VisibleWindTM initiative has sponsored the development and demonstration of a simple balloon tracking system
for low altitude wind profile measurements using laser rangefinders, a surveying station, and small (0.25 m
diameter) lightweight balloons. Experiments on balloon trajectories demonstrate that laser range detection (± 0.5 m)
combined with azimuth and elevation measurements is a simple, accurate, and inexpensive alternative to other wind
profiling methods. The maximum detection range has been increased to 2200 m using retroreflector tape on the
balloons. Nighttime tracking is facilitated by low power LEDs. Small balloons with low ascent rates and Reynolds
numbers are preferred to avoid the large trajectory fluctuations previously observed with large balloons. Under
conditions of "light and variable winds", the wind profile features observed by VisibleWindTM include the frequent
onset of shear at altitudes 100 -200 m, 1-3 m/s velocity transitions across atmospheric layers only 10 -20 m thick,
and rotation of wind direction exceeding 180 degrees in the altitude range 300 - 500 m. Wind speed and direction
results are compared with simultaneous sodar measurements. The profiling resolution is greatly improved using a
laser rangefinder, Impulse XL-200, with automatic coordinate and time recording; however, balloon tracking is still
man-in-the-loop. Planned improvements include automation of the tracking system itself, so trajectory points are
collected automatically at 1 Hz or faster. This ValidWindTM system is a precise and adaptable means for
characterizing highly variable wind fields for wind energy, micrometeorology, and air quality studies.
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