20 January 1997

Dear MODIS PIs and others,
As mentioned in earlier emails and at the MODIS Science Team meeting, we
have been aggressively addressing the need to assess our validation test
site sampling strategies (both ground and aircraft-based) and instrument
requirements.  The following describes the information we learned from the
Jornada Experimental Range (USDA-ARS) and LTER personnel during their 96-97
Science Meeting on January 13-15, 1997 in Las Cruces, NM.

Three AM-1 sensors were represented at this meeting, including MODIS (Wim
van Leeuwen, Faiz Rahman and Jeff Privette), MISR (Jim Conel), and ASTER
(Kurt Thome).  Eleven scientists from the USDA-Agricultural Resource
Service (ARS), some jointly associated with the LTER program, were also in
attendance.  Note the 72000 ha JORNEX area is owned by the USDA-ARS; the
LTER personnel work in a fairly small subarea.  About 55000 ha of the total
area is accessible.

Before discussing details, I'll jump to our joint (MODIS, MISR and ASTER)
recommendation.  We are proposing an approximately 10-day prototype
validation exercise at JORNEX in late May/early June (actual dates T.B.D.)
of this year.  This month coincides with their rather extensive previous
data collection efforts in 1995 and 1996, and also with their planned
Jornada AVIRIS and possibly TIMS flights.  It appears that personnel from
all three teams, USDA-ARS and LTER can converge on the site at this time,
and extensive aircraft data can be collected.  We will try to piggyback
AirMISR and MAS on the planned Jornada AVIRIS flight, and again piggyback
on the planned Lunar Lake calibration flights and have the ER-2 sweep down
and cover Jornada.  We believe that if we are to have a standardized and
valid data collection strategy for a globally distributed set of EOS test
sites, the proposed exercise is critically important and the need
immediate.  We have promised an official notification of our intention to
conduct this exercise to Jornada personnel by January 31.  Please read on
with that in mind.

Site description.
The Jornada is a very large valley (roughly 50 miles x 100 miles) in
southwestern NM.  Although bounded on the east and west by mountains, the
valley is extremely flat--among the flattest areas in the U.S. I have seen.
The area is slowly undergoing a landcover change from grassland to
shrubland (predominately mesquite).  The probable cause for this is
overgrazing near the turn of the century.  Some areas continue to be
grazed.  Because of this landcover change, three distinct areas exist:
grassland, shrubland, and transitional (mixed grassland and shrubland).
Currently, there are approximately 8000 ha of grassland, 12000 ha of
transitional, and 35000 ha of brushland.  In the brushland area,
approximately 70% is mesquite, 20% creosote, and 10% tarbush-dominated.
The mesquite area, which is "most transformed" from the original grassland
state, contains sand dunes in and around all shrubs.  The dunes can be
rather large--2 to 3 meters high--making this particular section difficult
for field work.

The area is very arid, and as such both the grasses and shrubs are sparse
in areas, and the average leaf area index is low (~0.5 average).  As is
typical of such environments, the woody-to-herbaceous ratio is relatively
high.  The area is driest in the spring, and assumes it highest LAI values
in September following the late summer monsoons.  There are virtually no
manmade structures in the whole area, except for a few unpaved roads, some
data towers, and some fences.  Thus, contributions from non-target
components in remote sensing data should be very small.

Previous data collection.
The primary science conducted by the ARS personnel concerns energy fluxes
of the different land cover types.  Three major experiment sites, one in
each of the landcovers, have been defined and studied.  The grassland site
currently contains a short met flux tower, the shrubland site contains a 10
m met tower, and the transitional site contains a 100 foot tower.  A
Jornada truck with a 105-foot cherrypicker is also readily available.

At previous times, ARS has collected both eddy correlation and bowen ratio
data at one or more sites; some bowen ratio and CO2 data continues to be
collected.  Moreover, they are interested in relating the fluxes to remote
sensing data, and have thus collected a fair amount of reflected and
thermal remote sensing data (including airborne, AVHRR and TM data), and
airborne laser data to help quantify the surface roughness.  Most of this
data was collected over the last two years (in May and September).  In
addition, they have collected surface temperature, LAI, ground cover
fraction, ground cover height, and NPP data during these months.  An
extensive comparison of 12 different net radiometers has also been
conducted at Jornada.  I can fax interested persons the data list that ARS
has provided to us.

EOS Prototype Validation Exercise.
After visiting the sites, our impression was that the shrubland site was
too heterogeneous to work effectively, particularly given the small dunes
associated with the shrubs.  The transitional site appeared a possible
albeit risky site if the sole point of focus.  However, the grassland site,
worked with the cherrypicker in place of a large tower, appeared very
reasonable.  In combination, the transitional and grassland sites would
seem span a range from more difficult (more experimental) to easier (more
conventional) in terms of data collection, reduction, and analysis.

We propose that a short but reasonably intensive data collection effort be
conducted collaboratively among MODIS, MISR, ASTER, USDA-ARS and LTER
personnel in May.  In this effort, we would collect remote sensing data
over different spectral, angular and spatial ranges with AirMISR, MAS,
AVIRIS, an Exotech radiometer (small aircraft) and possibly TIMS.  These
data sets could be collected over most of the JORNEX area, and should
adequately address issues of scaling, etc.  Second, we propose that a CIMEL
BRDF/sunphotometer be mounted at the top of the 100-foot transitional
tower, with a second CIMEL mounted in the cherrypicker at the grassland
site.  A PARABOLA instrument provided by MISR would be co-located in the
cherrypicker.  The horizontal and vertical mobility of the cherrypicker
should allow an extremely valuable opportunity to assess the tower
measurement strategy, plus extensive comparison between data from CIMEL,
PARABOLA, AVIRIS, MAS and AirMISR.  Finally, ground crews collecting
LAI/fAPAR/surface temperature data on transects at the two study sites can
be used in combination with the aircraft and tower data to help validate
sampling and scaling strategies.  Various data for atmosphere
characterization would also be collected.  A more complete list of proposed
equipment, with the responsible partner listed in parenthesis, is below.

We took a large number of photographs of these sites, and some are now
available at http://pratmos.gsfc.nasa.gov/~justice/modland/valid.html.
While the plan clearly cannot contain significant detail at this point, we
request that you review this proposal and reply to this email with your
comments and approval/disapproval.  Feel free to contact any of us (listed
above) for further details.  Site-specific questions may be best addressed
to Kris Havstad (LTER & USDA Jornada Experimental Range) at
khavstad@nmsu.edu, Al Rango (USDA Hydrology Lab, Beltsville, MD) at
alrango@hydrolab.arsusda.gov, Bill Kustas (USDA Hydrology Lab, Beltsville,
MD) at bkustas@hydrolab.arsusda.gov, or Jerry Ritchie (USDA Hydrology Lab,
Beltsville, MD) at jritchie@hydrolab.arsusda.gov.

We look forward to hearing from you.

Proposed Prototype Validation Exercise '97a
Jornada Experiment Range
May 15-25, 1997

(note: investigators able to provide instruments listed with "?" after them
should please identify themselves)

Focus sites: grassland, transitional

General approach:
        Collect BRDF (CIMEL) and thermal radiometry data from transitional
site tower, while ground crews conduct LAI/fAPAR transects;
        Collect BRDF data (CIMEL and PARABOLA) at different heights from
cherrypicker at grassland site, while ground crews conduct
LAI/fAPAR/radiometry transects;
        Collect energy and CO2 flux data for NPP evaluation;
        Release radiosondes for atmosphere characterization;
        Collect high altitude (ER-2) MISR and MODIS simulator data over all
sites;
        Collect low altitude radiometry data for scaling and site
characterization;
        Collect satellite data.

Required equipment for validation of surface reflectance (BRF/atmospheric
correction), vegetation indices, BRDF, albedo, LAI, fAPAR, NPP, and surface
temperature:

Transitional site:
100' fixed tower
        Everest thermal radiometer, insulated - surface temperature (ARS)
        CIMEL sunphotometer - BRDF, surface reflectance (NASA)
        broadband pyranometer - albedo (?)
ground transects
        Licor LAI-2000 - LAI (LTER)
        ceptometer - fAPAR (Uof A)

EC flux tower - NPP (ARS) - needs discussion with S. Running
radiosondes - surface reflectance (JPL, UA-ASTER)

Grassland site:
105' mobile cherrypicker truck
        CIMEL sunphotometer - BRDF, surface reflectance (NASA)
        Sensit PARABOLA - BRF, BRDF, HDRF, BHR, surface reflectance (JPL)
        albedometer - spectral albedo (JPL)
ground transects
        Licor LAI-2000 - LAI, VI (LTER)
        Licor LAI-3000 leaf processor - LAI destructive validation (LTER/ARS)
        ceptometer - fAPAR, VI (UA-MODIS)
        portable thermal radiometer - surface temperature (UCSB, UA)
        standing biomass weighing/assessment - NPP (ARS/LTER)

Bowen ratio + CO2 IRGA - NPP (ARS) -- (possible; discussion w/ S. Running
needed)

All sites:
ASD spectrometer with integrating sphere - VI, LAI, fAPAR (NASA, UA-ASTER)
GIS receivers (?)
two-way radios and/or portable telephones (?)

Remote sensing equipment:
ER-2 AirMISR + MAS - basic instrument simulators (JPL- 50% probable
piggybacking        on Lunar Lake calibration flights)
Cessna with Exotech 4 band radiometer, tiltable mount - scaling, BRDF (UA)
Pilotless ASD - scaling, site characterization (NASA)
ER-2 AVIRIS (+AirMISR,MAS,  stereophoto?) - scaling (ARS flight: between
        4/15-5/15)
Cessna Citation TIMS - surface temperature (ARS; out of Las Vegas/DOE)

AVHRR - MODIS simulation (NASA)
Landsat 5 TM - ASTER simulation, scaling (UA-ASTER)
SPOT HRV - ASTER simulation, scaling (UA-ASTER)
GOES - temporal variation (NASA)

Additional equipment available:
2 Everest thermal radiometers (UA-ASTER)
4 Exotech 4 band shortwave radiometers (UA)
Barnes MMR radiometer (UA-ASTER)

Pre-study activities/timeline
January 31 - Decision to conduct a May/June study
February 15 -  satellite data ordering
March 1 - aircraft coordination and commitments
March 15 - instrument order/procurement (any missing from above list -
pyranometers?)
March 31 - mount CIMEL sunphotometer/BRDF on fixed tower
April 15 - campaign definition, strategy, participation document (draft)
May 1 - LAI/fAPAR sampling strategy coordination

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