The Moderate Resolution Imaging Spectroradiometer (MODIS) Atmosphere Data Handler software converts the HDF data to ASCII format, and outputs: (1) atmospheric profiles of temperature and dew point and (2) total precipitable water. Quality-control data are also considered in the export procedure

Anantharaj, Valentine

Fitzpatrick, Patrick

NASA Technical Reports Server

NASA Tech Briefs, December 2008 7
A method of incorporating informa-
tion, acquired by a multibeam laser or
radar altimeter system, pertaining to the
distance and direction between the sys-
tem and a nearby target body, into an es-
timate of the state of a vehicle upon
which the system is mounted, involves
the use of a faceted model to represent
the shape of the target body. In the orig-
inal intended application, the vehicle
would be a spacecraft and the target
body would be an asteroid, comet, or
similar body that the spacecraft was re-
quired to approach. The method could
also be used in navigating aircraft at low
altitudes over terrain that is rough
and/or occupied by objects of signifi-
cant structure.
Fundamentally, what one seeks to
measure is the distance from the vehicle
to the target body. The present method
is the product of a generalization of a
prior method of altimetry, in which the
target body has a simple shape repre-
sented by a spherical or ellipsoidal
model. In principle, the estimate of dis-
tance or altitude obtained by use of a
multibeam altimeter can be more robust
than that obtained by use of a single-
beam altimeter, but if the surface of the
target body has a complex and/or irreg-
ular shape, then it becomes more diffi-
cult to define the distance and compute
the distance from readings of a multi-
beam altimeter.
The faceted shape model of the pres-
ent method facilitates the definition and
computation of distance to a target ob-
ject having almost any shape, no matter
how irregular and complex. The use of
faceted shape models to represent com-
plex three-dimensional objects is com-
Multibeam Altimeter Navigation Update Using Faceted 
Shape Model
The model is applicable to a body having almost any complex shape.
NASA’s Jet Propulsion Laboratory, Pasadena, California
MODIS Atmospheric Data Handler
Stennis Space Center, Mississippi
A number of science data sets are derived
from the observations of the Moderate
Resolution Imaging Spectroradiometer
(MODIS) instrument onboard NASA’s
Terra and Aqua satellites. These data
typically contain information on re-
trieval techniques, quality-control flags,
and geo-referencing information.
These datasets, distributed in HDF (Hi-
erachical Data Format), must be fur-
ther processed to extract relevant infor-
mation for weather analysis studies and
numerical models input. The MODIS-
Atmosphere Data Handler software
converts the HDF data to ASCII format,
and outputs: (1) atmospheric profiles
of temperature and dew point and (2)
total precipitable water. Quality-control
data are also considered in the export
procedure.
The package currently consists of pro-
grams to process the MOD05 and
MOD07 data products from MODIS.
The software is written using the C pro-
gramming language and contains Make-
files for easier compilation and installa-
tion.  The MODIS-ADH software helps
ease the overhead involved in data pro-
cessing so that the numerical modelers
may concentrate on their science and
modeling tasks rather than manipulat-
ing data for their models.
This program was written by Valentine
Anantharaj and Patrick Fitzpatrick of the
Northern Gulf Institute at Mississippi State
University for Stennis Space Center.
Inquiries concerning rights for its commer-
cial use should be addressed to:
Mississippi State University
Northern Gulf Institute
BLDG 1103, Room 233
Stennis Space Center, MS 39529
Phone No.: (228) 688-1157
Fax: (228) 688-7100
E-mail: val@gri.msstate.edu
Refer to SSC-00267, volume and number
of this NASA Tech Briefs issue, and the
page number.
secutive radar profiles are offset slightly
(by amounts much less than Δr) with re-
spect to each other according to the rel-
ative change in geodetic altitude. As a
consequence, in a case in which the sur-
face area under examination is homoge-
nous (e.g., an ocean surface), a se-
quence of consecutive radar profiles of
the surface in that area contains samples
of the surface response with range reso-
lution (Δρ) much finer than the range-
bin increment (Δρ << Δr). 
Once the high-resolution surface re-
sponse has thus become available, the
profile of surface clutter can be accu-
rately estimated by use of a conventional
maximum-correlation scheme: A trans-
lated and scaled version of the high-res-
olution surface response is fitted to the
observed low-resolution profile. The
translation and scaling factors that opti-
mize the fit in a maximum-correlation
sense represent (1) the true position of
the surface relative to the sampled sur-
face peak and (2) the magnitude of the
surface backscatter.
The performance of this algorithm has
been tested on CloudSat data acquired
over an ocean surface. A preliminary
analysis of the test data showed a surface-
clutter-rejection ratio over flat surfaces of
>10 dB and a reduction of the contami-
nated altitude over ocean from about 1
km to about 0.5 km (over the ocean).
The algorithm has been embedded in
CloudSat L1B processing as of Release 04
(July 2007), and the estimated flat sur-
face clutter is removed in L2B-GEOPROF
product from the observed profile of re-
flectivity (see CloudSat product docu-
mentation for details and performance at
http://www.cloudsat.cira.colostate.edu/
dataSpecs.php?prodid=1).
This work was done by Simone Tanelli,
Kyung Pak, Stephen Durden, and Eastwood Im
of Caltech for NASA’s Jet Propulsion Laboratory. 
The software used in this innovation is
available for commercial licensing. Please
contact Karina Edmonds of the California In-
stitute of Technology at (626) 395-2322.
Refer to NPO-44873.
https://ntrs.nasa.gov/search.jsp?R=20080048051 2019-08-30T05:47:15+00:00Z


MODIS Atmospheric Data Handler

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