2011 - Cooperative Institute for Research in Environmental Sciences ...

Figure 1: Global image of the Radiance Calibrated Nighttime Lights
from 2010 DMSP F16
Figure 2: Ho Chi Min City, Vietnam. The first image shows the Operational
Stable Lights data where the urban core is saturated. The second
image is the Radiance Calibrated data where the urban core is resolved.
The radiance of the brightest pixels is measured to be a factor of about
12 larger than the saturated values.
Advanced Network (APAN) conference proceedings. In
order to create this product, a generalized method was created
for processing other years.
Product: Ziskin, D, KE Baugh, FC Hsu, T Ghosh, and CD
Elvidge (2010), Methods used for the 2006 radiance lights,
Asia-Pacific Advanced Network conference.
Milestone 2: Develop a methodology for determining gain
settings on DMSP OLS operational data for satellites F16
and F18.
Due to the fact that the gain settings are not stored in
the DMSP Operational Linescan System (OLS), smooth
resolution visible band data has been a barrier toward intercomparability
of the OLS data. This work was the first step
toward the goal of OLS data calibration (see Milestone 3).
Figure 3: Comparison of the recorded OLS visible band gain values and
the software-reconstructed values for the last sample in each scanline of
an F16 fine-resolution orbital segment.
126 CIRES Annual Report 2011
Software was created to reconstruct the DMSP-OLS gain
settings for any orbital swath of data from satellites F16 and
F18. The software is a recreation of the onboard along-scan
gain control algorithms that the OLS uses to set the visible
band gain. Onboard constants to the gain algorithm are
modified weekly via Payload Activation Messages (PAMs).
The PAMs were obtained and converted into a temporal
database of gain constants that is accessed by the gain reconstruction
software. The OLS fine-resolution datastream
records the gain for the last sample in each scanline. This
sample of recorded gains was used for software validation.
Milestone 3: Development of a robust and effective calibration
method for the DMSP OLS time series based on
reflected moonlight from desert surfaces for satellites F16
and F18.
Moonlight reflected off of desert surfaces was measured
with the DMSP F16 and F18 satellites. The satellite gain
settings were estimated for each overpass (see Milestone
2). This allowed us to determine the instrument’s response
and calculate an ‘uncalibrated radiance.’ We also modeled
the expected radiance using an advanced radiative
transfer model (MODTRAN). The comparison between
the uncalibrated radiance from the instrument and the
modeled radiance has yielded a compelling relationship.
Work along this promising line will continue with the goal
of developing an absolute calibration of the OLS.
Figure 4: The Uyuni
Salt Flats in Bolivia
in full moonlight.
Figure 5: The radiance that the DMSP F18 satellite observed is simulated
by the MODTRAN radiative transfer model.