# Presentation: 714144

## Overview of HARLIE Measurement Capabilities

- David Miller1, Geary Schwemmer2, Sangwoo Lee1, Tom Wilkerson3
- 1Science Systems and Applications, Inc.
- 2NASA Goddard Space Flight Center
- 3Utah State University
- http://harlie.gsfc.nasa.gov

**Notes:**
Good morning, I’m David Miller with Science Systems and Applications, Inc. at NASA/Goddard Space Flight Center, and I will be introducing you to the Holographic Airborne Rotating Lidar Instrument Experiment, or HARLIE. My goal today is to give you basic understanding of the HARLIE lidar instrument and its capabilities, some of which we believe will be useful in the air quality field. 

Listed with me are some of my colleagues; Geary Schwemmer is the HARLIE instrument PI, Sangwoo Lee, also from SSAI, and Tom Wilkerson from Utah State University.

Information on HARLIE as well as quicklooks of the data collected during the various field campaigns is available on our website at: harlie.gsfc.nasa.gov

## Overview

- Data products & examples
- Field study highlights
- Current work
- Summary

**Notes:**
I’ll begin with a description of HARLIE instrument; it’s specifications and method of operation. Next, I’ll cover the some of the data products available using HARLIE and a couple examples of HARLIE measurements. Then I’ll give a brief overview of the field campaigns that we have participated in over the past few years. In particular, I’ll show some of the measurements from the recent SERDP sponsored study where HARLIE was used to profile dust plumes. I’ll highlight some of our current tasks and follow up with a summary.

This pictures shows some of the participants in the HARGLO-2 field campaign.

## Technical Data

- Receiver: *40 cm diameter, f/2.5 volume phase transmission HOE, 45° diffraction angle, effective collection area 1064 cm^2, 200 μrad field-of-view, 0.5 nm bandpass*
- Detector: *Geiger mode Silicon Avalanche PhotoDiode** *

**Notes:**
HARLIE is very similar to a conventional aerosol backscatter lidar with the exception of the receiver telescope. In place of a standard telescope, a 40 cm diameter transmission holographic optical element, or HOE, is used as the collecting and focusing aperture on HARLIE. This is a picture of the HOE used on HARLIE (point to HOE). The HOE has a 45-degree diffraction angle and is rotated during operation resulting in a conical scan of the atmosphere. The use of the HOE greatly reduces the mass and complexity of the instrument since we need only rotate the HOE instead of scan mirror or telescope to achieve multi-direction profiles. More economical. This is especially beneficial when using the instrument on an aircraft. 
Also listed are the laser and detector specifications. A more complete list of the instrument specifications is available on our web site.

The bottom picture shows HARLIE in its original configuration, outside the trailer, with the transceiver on the right and the equipment rack on the left which holds the data system, laser power supply and chiller. 

## Optical system

**Notes:**
The picture on the upper left shows the optical layout within the instrument body. The laser is the red cylinder, the various steering mirrors, and the HOE is located at the top.

On the lower right is a animation showing the light path within HARLIE. The black cylinder (here) is the laser. The beam first passes through a diverging lens (point) to f-match the beam to the HOE. Using three steering mirrors (point), the diverging beam is directed to the center of the HOE where it is collimated and diffracted at 45 degrees. Due to the nature of the HOE, only light from the same direction as the outgoing beam is collected and focused by the HOE. An optical fiber sits at the HOE focus and transmits the backscattered light to a filter and detector package located outside of the instrument. 

## Scan Patterns

- Continuous Rotation

- Static Mode

- Sector Scan

- Step and Stare

- One variation

**Notes:**
Here is a selection of the various scan patterns that HARLIE is capable of performing. The most common operating mode is the continuous rotation mode shown at the upper-left where the beam continuously sweeps at a constant rate. HARLIE can also operate in static mode where the beam is fixed. The beginning and end scan angle and rate can be specified in the sector scan mode shown here. Also shown is the step-and-stare mode where the beam is moved to a specific direction and dwells for a period of time before moving to the next position. The instrument itself can be tilted allowing the scan axis to be positioned at any point from horizontal to vertical. This allows for a large variety of scan configurations. The last figure depicts one such variation with the scan axis at 45 degrees resulting in a conical scan that goes from horizontal to vertical.

## Data Products

- Real-Time Aerosol Backscatter Profiles

- Boundary Layer top

- Entrainment Zone Thickness

- Cloud Bottom Heights

- Wind Profiles

**Notes:**
Real-time aerosol backscatter profiles are the standard data product in which all other products are derived. This image shows a time series of backscatter profiles fpr a 3.5 hour period. The height scale is from 0 to 6 km. The yellows and whites represent the strongest backscatter returns. Also available are several boundary-layer properties such boundary-layer top, entrainment zone thickness and cloud bottom heights. Using a technique developed by Tom Wilkerson and his students at USU, it is possible to extract wind vectors from HARLIE data. All of the products are available with a range resolution of 30 meters.

## Bore wave investigation

- 0o

- 90o

- 180o

- 270o

**Notes:**
In September of 2000, during the WVIOP experiment, a bore wave passed over the ARM CART site in Lamont, OK. This bore wave is visible in the four panels shown here. The panels are time/altitude plots of relative backscatter with the yellows being the maximum. The time going from 330 to 700 UTC and altitude up to 6km. Each panel shows the profiles from one of the four compass points; north, east, south, and west. The leading edge of the bore is visible here as well as the subsequent undulations. The yellow portions are clouds caused lifting at the leading edge of the bore. Notice the differences in the aerosol and cloud structures in the 4 different directions. The conical scan gives us the ability to see variations across a region of interest.  

## Data Visualization

**Notes:**
This is an animation of several hours of HARLIE data collected during the HOLO-1 field mission. The scan cone is visible with the rings on the cone marking altitude with a maximum of 6km. The yellow arrow points towards north. The advection of aerosols through the cone is easily seen, especially at the lower altitudes. Some of interesting features to notice is the sinking motion of the aerosol layers as well as the directional shear. Kelvin-helmholtz waves are also briefly visible. 

## HARLIE Field Study History

**Notes:**
HARLIE’s first light was in January of 1998, and then it was flown in a series a short test flights in the spring of that year on NASA’s short lived Fairchild 27 aircraft. HARLIE worked well during its airborne test flights, but has seen extensive ground based use since that time.

The HOLO field campaigns were designed to give HARLIE a thorough workout and to develop a wind profiling technique conceived by Tom Wilkerson. The first of these was held at the Space Dynamics Lab in Logan Utah, and the second at Saint Anselm’s College in Manchester New Hampshire where our first holographic lidar, PHASERS, resides. We used HARLIE in conjunction with other lidars, and SKYCAM, a visible wide-angle video camera and recorder aimed at zenith to record visible cloud imagery over roughly the same footprint as HARLIE’s scan. The SKYCAM recordings have been used to generate independent cloud-tracked wind measurements with the aid of lidar altitude assignments for the clouds visible on the camera recordings.

During HOLO1&2 HARLIE collected data over a dozen days of operations, during which the instruments had to be continuously wheeled in and out of buildings, suffering through dust, pollen, rain, snow, temperature extremes causing frost on optics to electronics overheating and failing.

## HARLIE Field Study History

**Notes:**
So to address these issues we installed HARLIE in a small environmentally controlled trailer. HARLIE was then totally enclosed, scanning up through a 50cm diameter window in the roof of this trailer. We exercised this new all weather capability during the Atmospheric Radiation Measurement Program’s Water Vapor Intensive Operating Period (WVIOP) in the autumn of 2000.

Encouraged by the results of our wind retrievals, we began a program of systematic comparisons between HARLIE and other wind measuring systems, especially the NASA GLOW Doppler Lidar. After a few brief comparisons between GLOW and HARLIE, last November we set out for NASA Wallops Flight Facility for the second wind comparison campaign dubbed HARGLO-2. We also hired the launch of a number of GPS radiosondes to take advantage of their greater accuracy in wind retrievals over conventional Loran tracked sondes launched by the National Weather Service.

We spent the last 2 months participating in the International H2O Project (IHOP) in conjunction with many other instruments, to study the role of moisture in the evolution and initiation of convection leading to severe storms in the Oklahoma panhandle region. While HARLIE does not measure water vapor, it provided supplemental measurements as outlined earlier.

## SERDPApril 12-26, 2002Fort Bliss, TX

**Notes:**
In April, we participated in an SERDP sponsored study with members of the Desert Research Institute to help quantify the atmospheric aerosol loading generated by military vehicles during training exercises. The study was held at Fort Bliss, TX, in April of this year. HARLIE was tilted so the scan axis was horizontal, requiring us to operate with the back of the trailer open. The upper left picture is the back of the HARLIE trailer with the instrument peeking out through the tarp. The upper right picture shows one of the particle sampler towers at the DRI site. It seems someone forgot to look at the map in the lower picture.

## Measurement Geometry

**Notes:**
HARLIE was located approximately 2 km to the west of the DRI site. This picture (left) shows a single scan with the east leg of the scan intersecting the DRI site. The maximum range of this picture is 3km and again this is relative backscatter with the bright oranges being the strongest returns. A dirt road runs nearly north-south on the west side of the DRI site and is shown as the line.  This scan took place less than a minute after a vehicle had passed the DRI site and the dust plume is visible.

## Plume Cross Sections

**Notes:**
This is a 10 degree segment of the east leg of our scan. The image is of backscatter intensity with the greens and yellows being the strongest returns. The range goes from zero to 3km and the vertical extent at 3km is approx. 500m. This image shows the segment shortly after a vehicle passed the DRI site. The next image is one minute later. The plume is noticibly larger. An again this time 2 minutes later. The complex evolution of the plume is evident.

## Azimuth Scan Axis

**Notes:**
Previously, HARLIE was mounted on a rigid fork mount that allowed the instrument to be tilted in the vertical axis. On the right is a model of HARLIE integrated on the new fork mount that will allow HARLIE to rotate in azimuth as well. By tilting the scan axis to 45 degrees, and rotating in azimuth, we can perform hemispheric scans as depicted in the upper left image. Another potential application is the profiling of effluent plumes. If we operate the HOE in small angle mode, and scan back and forth with the azimuth axis, we could profile an plume at numerous downwind distances from a stack. 

## Current work

- Calibrate HARLIE data – backscatter and extinction coefficients
- Aerosol mass loading
- Characterize plume extent and dispersion
- Characterize background aerosols
- Integrate the new azimuth scan axis

**Notes:**
Our current agenda focuses on calibrating the data collected during SERDP. With the help of the instruments  present at the DRI site, we will calibrate the backscatter values from HARLIE and derive extinction coefficients. We also plan to determine the aerosol mass loading using the particle sampler data collected at the DRI site. Characterizing the plume extent and dispersion as well as the background aerosols is also a goal.

The new azimuth scan axis has been constructed and we are now incorporating it into the data system. 

## Summary

- Instrument overview
- Data products
- Field studies
- Current work

**Notes:**
Employing a HOE in place of a conventional telescope, HARLIE has proven to be a very succefull lidar system.

HARLIE has been used in a variety of field operations proving that it is capable multi-month operations. 

## Slide 17

## Slide 18

## Wave Image of HARLIE Data

**Notes:**
The HARLIE method of wind profile retrieval uses time series of backscatter as a function of scan azimuth angle.. The retrieval technique is essentially a time-lag correlation technique done on each altitude level in the data record independently. Valid retrievals are obtained where there is sufficient structure motion in the aerosol scattering field. Two methods of retrieval have been developed at Utah State University. One a graphical technique, and one a computer automated numerical technique. The graphical technique is illustrated in this image. We call these wave images because of the wavy lines produced by the motion of scattering structures. The circle of data at one altitude is “unwrapped” into a line and placed on the vertical axis. Successive scan lines at the same altitude are lined up along the horizontal axis.  Imagine the edge of a cloud or other scattering feature advecting through HARLIE’s scan cone of regard. It will generate a sinusoidal wave pattern in this type of plot. A duplicate of each scan is placed next to the original to show two periods of the cosine waves to make them easier to visualize. An interactive graphical user interface displays a cosine curve, which is adjusted in amplitude and phase to “best fit” the patterns in the HARLIE data. The slope of the linear portion of the sine wave is indicated by the straight line, and from this the wind speed is obtained automatically. The phase of the left hand peak of the sine wave will indicate the wind direction on the azimuth scale of the Y axis. Several fits are made to a portion of the data image, about 30 minutes worth, and the mean and standard deviation of the wind speed and direction calculated. Because HARLIE uses data from a large circular area extending over several km (diameter=2x altitude), we believe it may better represent the mean bulk wind within the circle as opposed to in-situ sensor measurements such as those carried aloft by radiosonde balloons. An automated numerical algorithm was produced to obtain these results in a faster and more consistent manner. The island vortex shedding seen in the background satellite photograph illustrates one phenomenon that may create problems for us in this type of analysis, as separate parts of HARLIE’s scan may have very different wind vectors due to small scale turbulent features or wave propagation speeds leading to invalid or multiple solutions.

## Aerosol Backscatter and Extinction Coefficients

**Notes:**
Using an independent measure of optical depth, HARLIE data was calibrated and aerosol backscatter and extinction coefficients were retrieved. The plot on the left is of total backscatter coefficient with a scale from 10-6 to 10-2 inverse kilometers and 0 to 20 km. The plot on the right is of aerosol extinction coefficient with a scale from 10-5 to 1 and the same height scale.