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Top Level Goals of the Near-Space BalloonWinds Program
- Demonstrate Multi-Order Photon Recycled Direct-Detection Fringe Imaging from a high altitude (30 km) balloon to measure wind velocities throughout entire troposphere.
- Demonstrate technology under as many atmospheric conditions as possible; i.e. high and low clouds, high and low winds, variable boundary layer aerosol conditions, day and nighttime
- Validate LIDAR models for a high altitude downward looking platform
The BalloonWinds program is a NOAA-funded joint development effort between Michigan Aerospace Corporation and University of New
Hampshire (UNH) to develop a space precursor Doppler wind lidar that will be flown on a high altitude balloon. The primary goal of
the BalloonWinds near-space initiative is to validate photon recycled 355 nm direct detection Doppler wind LIDAR technology from a
platform looking down from the top of the atmosphere. The balloon flight altitude will be ~30 km (100k ft), which is above the
troposphere, and each of the 4 planned missions will have at least 8 hours of data collection time at the float altitude. At the 30
km float altitude the atmospheric pressure is ~5 millibar and the temperature -45 c, which required the instrument payload components
to be sealed and thermally stabilized from the environment. A design emphasis was placed on rugged and compact packaging of the
instrument system components due to the vibe and shock environment encountered during launch and landing of the balloon system.
Figure 5 shows the laser (a ruggedized, diode-pumped system from Fibertek) and telescope system components of BalloonWinds.
The BalloonWinds interferometer system is shown in Figure 7.
Near Space Balloon Demonstration Team and Responsibilities |
| University of New Hampshire (UNH)-System/Integration |
| Thermal Management |
| Power Distribution and Telemetry System |
| Gondola Design and Systems Engineering |
| Michigan Aerospace Corp. (MAC)-Instrument |
| Instrument Systems Engineering |
| Interferometer and Environmental Packaging |
| Laser/Telescope System and Environmental Packaging |
| Instrument Control System |
| Control Electronics Packaging |
| Raytheon- Santa Barbara Remote Sensing (SBRS) |
| Telescope and Laser Development Oversight |
| Fibertek |
| Diode Pumped Laser |
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Figure 1 |
Mission Environment and Flight Schedule
| Flight # |
Objective |
Atmospheric Condition |
Mission Date |
| 1 |
Nighttime Concept Demonstration |
Night- Clear Air |
June 2006 |
| 2 |
Daytime Concept Demonstration |
Day- Partly Cloudy |
June 2006 |
| 3 |
Full System Demonstration |
Day and Night Partly Cloudy |
September 2006 |
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Mission and Program Characteristics
| Program Sponsor |
NOAA |
| Balloon Launch Site |
Holloman Air Force base in New Mexico |
| Float Altitude of Balloon |
>100,000 ft. |
| Measurement Range |
Clear night skies: (float – 2 km) to Ground)
Cloudy night: (float – 2 km) to (cloud top + 1 km) |
| Wind Measurement Accuracy |
< 3.0 m/s Line-of-sight during clear night sky |
| Elevation of Telescope |
45˚ ± 1˚ below horizontal |
| Range Gate Size |
1 km above 3 km |
| LOS Profile Measurement Frequency |
≥2 seconds |
| Active Wind Collection Time at Float |
>4 hours |
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Near Space Flight Gondola |
Figure 2 |
Laser-Telescope Subsystem
- Laser Head & Control Electronics
- Beam Delivery and Beam Steering
- Independent telemetry data acquisition system for environmental monitoring and power control.
- Liquid to air heat exchangers regulate internal temperature
- Pressure maintained to 1.0 ATM
- Telescope and laser coupled through common interface (GLTI)
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Figure 3 |
Figure 4: Diode-Pumped Solid State 4 watt 355nm Laser
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Figure 5: Integrated Laser-Telescope System
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Figure 6: Space-Class 50 cm Telescope
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Sealed laser chamber contains laser head, laser electronics, beam delivery optics and thermal control system.
Laser-telescope alignment maintained to < 10 micro-radians.
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Interferometer Subsystem
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Figure 7: Top down view of BalloonWinds dual channel space prototype interferometer prior to shipment. As seen on right and left
side of the picture are the tunable Fabry-Perot Etalons.
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Figure 8: Side view of BalloonWinds interferometer integrated equipment plate prior to installation into pressure vessel.
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Figure 9: View of BalloonWinds interferometer system sealed in pressure vessel for flight.
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Figure 10: Side view of interferometer with side down.
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Predicted Measurement Performance
The system efficiency is based on a combination of measured values as well as manufacturer
specified values for the various optical components in the system. The plots shown in figure 4 below are the counts detected at the
CCD for 12 seconds of integration as well as the aerosol to total scattering ratio at 355 nm for each of the different models used to
make performance predictions. The simulations were performed using 5 different models of varying aerosol concentrations; model 9 was
a case with no aerosol backscatter contribution. As seen from the plots shown in Figure 6 there is a discontinuity at 3km, which is
due to the increased altitude resolution from 1 km to 0.25 km for measurements ≤3km. Evident from the plot of detected counts,
the initial return from the instrument does not start for ~2 km in altitude below the instrument, where the laser beam and telescope
field of view overlap.
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Figure 14: Detected counts at CCD for 12 seconds of integration (left) and aerosol models (right) used in
performance predictions. The aerosol models are plotted as aerosol to total backscatter at 355nm. The various aerosol models
used to generate the plots are labeled in the plots, Model 9 does not have any aerosol scattering in it |
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Figure 15 plots the current best estimate performance predictions for the BalloonWinds instrument for the aerosol models shown in
Figure 14. The two cases plotted in Figure 15 depict the expected wind errors for the molecular channel without light recycling, whereas
the second includes 3 recycles on the molecular channel and 3 on the aerosol channel. Note that in both cases accuracies of less than
3 m/s can be expected for the entire altitude range; the sharp increase at 27.5 km is where the interaction region, hence the initial
return, of the instrument begins. From an evaluation of Figure 8 the contribution of photon recycling to the reduction of wind error
is clearly seen, and is most prominent in the boundary layer. In all cases the wind accuracy is enhanced by ~30%; in regions of high
aerosol content the enhancement may be as high as 70% because of the increased sensitivity of the aerosol channel.
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Figure 15: Performance prediction without photon recycling (left), and with 3 recycles each on the molecular and aerosol channel (right). Simulations used a 12 second total integration time with 6 seconds of on-chip integration. The errors are reported as line-of –sight projected to the horizontal plane (LOSH). |
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