Two overlapping efforts help to characterize the GLM performance, the Post Launch Test (PLT) phase to validate the predicted pre-launch instrument performance and the Post Launch Product Test (PLPT) phase to validate the lightning detection product used in forecast and warning decision-making. This paper documents the calibration and validation plans and activities for the first 6 months of GLM on-orbit testing and validation commencing with first light on 4 January 2017. The PLT phase addresses image quality, on-orbit calibration, RTEP threshold tuning, image navigation, noise filtering, and solar intrusion assessment, resulting in a GLM calibration parameter file. The PLPT includes four main activities, the Reference Data Comparisons (RDC), Algorithm Testing (AT), Instrument Navigation and Registration Testing (INRT), and Long Term Baseline Testing (LTBT). Field campaigns are also designed to contribute valuable insights into the GLM performance capabilities. The PLPT tests each contribute to the beta, provisional, and fully validated GLM data

Bateman, Monte

Blakeslee, Richard J.

Buechler, Dennis E.

Goodman, Steven J.

Koshak, William J.

Mach, Douglas M.

Rudlosky, Scott D.

NASA Technical Reports Server

CHARACTERIZING THE GOES-R (GOES-16) GEOSTATIONARY LIGHTNING MAPPER 
(GLM) ON-ORBIT PERFORMANCE 
 
Scott D. Rudlosky1 
Steven J. Goodman2 
William J. Koshak3 
Richard J. Blakeslee3 
Dennis E. Buechler4 
Douglas M. Mach5 
Monte Bateman5 
 
1NOAA/NESDIS/STAR 
2NOAA/NESDIS/GOES-R Program Office 
3NASA/MSFC 
4UAHuntsville 
5USRA 
 
ABSTRACT 
 
Two overlapping efforts help to characterize the GLM 
performance, the Post Launch Test (PLT) phase to validate 
the predicted pre-launch instrument performance and the 
Post Launch Product Test (PLPT) phase to validate the 
lightning detection product used in forecast and warning 
decision-making. This paper documents the calibration and 
validation plans and activities for the first 6 months of GLM 
on-orbit testing and validation commencing with first light 
on 4 January 2017. The PLT phase addresses image quality, 
on-orbit calibration, RTEP threshold tuning, image 
navigation, noise filtering, and solar intrusion assessment, 
resulting in a GLM calibration parameter file. The PLPT 
includes four main activities, the Reference Data 
Comparisons (RDC), Algorithm Testing (AT), Instrument 
Navigation and Registration Testing (INRT), and Long Term 
Baseline Testing (LTBT). Field campaigns are also designed 
to contribute valuable insights into the GLM performance 
capabilities. The PLPT tests each contribute to the beta, 
provisional, and fully validated GLM data. 
 
Index Terms— Lightning, GOES-R, GLM, Calibration 
 
1. INTRODUCTION 
 
The first Geostationary Lightning Mapper (GLM) sits aboard 
the first satellite in the Geostationary Operational 
Environmental Satellite R-series (GOES-R; which became 
GOES-16 after reaching geostationary orbit on 29 November 
2016). The GLM is the first step in the operational space-
based observing constellation for continuous measurements 
of total lightning on a global-scale. It builds on a legacy of 
optical lightning observations from low earth orbit from the 
NASA Lightning Imaging Sensor (LIS) on the Tropical 
Rainfall Measuring Mission (TRMM, 1997-2015) and 
Optical Transient Detector (OTD) on the OrbComm-1 
satellite (1995-2000). The GLM on GOES-16 is the first of 
four instruments that will provide lightning mapping of most 
of the the western hemisphere through 2036. The initial 
check-out and post-launch testing is six months at 89.5° W 
longitude followed by a period of extended validation for 
GOES-16 only of an additional six months. Following the 
one year of post launch testing the GOES-16 satellite will 
replace the GOES-E (75W) or GOES-W (137W) satellites 
depending on the health of the geostationary satellite 
constellation at that time.  
The ground processing algorithms are an extension of the 
algorithms developed for the earlier OTD and LIS research 
instruments [2] (Mach et al. 2007). Concepts for the GLM 
have been explored since the early 1980s culminating with 
the single telescope design having high detection efficiency 
for total lightning with near uniform storm-scale spatial 
resolution owing to the variable pitch pixel detector array 
design [1] (Goodman et al. 2013). The high detection 
efficiency is made possible by the data telemetry bandwidth 
https://ntrs.nasa.gov/search.jsp?R=20170007464 2019-08-29T22:17:04+00:00Z
of 7.7 mbps. This allows the GLM to be set at more sensitive 
(lower) detection thresholds allowing up to 100,000 events 
per second (nominally 40,000 lightning events and the 
remainder noise) to be transmitted to the ground where the 
ground processing algorithms filter out the non-lightning 
events. 
 
The calibration and validation efforts are both critical and 
challenging because the GLM is the first instrument of this 
type to operate in geostationary orbit [1]. Pre-launch and on-
orbit checkout of the instrument performance and algorithms 
employs a variety of space, airborne, and ground-based 
instruments. Public, private, and international partnerships 
provide extensive lightning reference data sets for post-
launch testing and validation. The methodologies, validation 
tools, and correlative data needed during on-orbit checkout 
and for continued monitoring have been developed and tested 
well before launch. 
 
2. GLM CALIBRATION ACTIVITES 
 
Two overlapping efforts help to characterize the GLM 
performance: the vendor-led Post Launch Test (PLT) phase, 
and the Post Launch Product Test (PLPT) phase led by the 
GLM science team. A field campaign also contributes to 
GLM calibration and validation. This paper documents the 
calibration and validation plans and activities for the first 6 
months of GLM operations. 
 
2.1. Post-Launch Test Phase 
 
The PLT phase first addresses image quality and on-orbit 
calibration. GLM periodically collects snapshots of the 
average background radiance, and the vendor uses a PLT tool 
to extract and analyze background image metrics. The GLM 
also allows for on-orbit calibration where a macro in the 
GLM flight software can dial thresholds for the on-board 
instrument timing without ground commanding. Setting the 
Real Time Event Processor (RTEP) detection thresholds is a 
critical aspect of the PLT. The GLM identifies any positive 
change in the pixel radiance value that exceeds these 
programmable detection thresholds, so the RTEP must be 
tuned carefully. Continuous monitoring of the RTEP 
thresholds will be required to ensure optimal GLM 
performance. 
 
Image navigation and noise filtering are also integral to 
successful GLM operations.  User applications require GLM 
data to be properly navigated to earth-based latitude- 
longitude coordinates. The Coastline ID is a ground image 
processing algorithm applied to daytime background images 
from GLM that identifies coastlines to translate (x, y) to 
(longitude, latitude) for L1b lightning data. The ground-
processing algorithms (GPAs) include several filters that 
must be tuned with the GLM collecting data in orbit. The 
initial PLT tuning is performed on the GLM vendor’s GPA 
implementation. This process is aided by a PLT tool for 
slicing and displaying event data in time and space. Real-
time analysis of the contributions from the various filters 
along with longer term assessments help to ensure properly 
tuned filters.  The PLT also includes a Solar Intrusion 
Assessment. During eclipse season, direct solar illumination 
enters the GOES-16 GLM optics and reaches almost to the 
focal plane. Approaches for quantifying the degradation (as 
well as other data quality attributes; e.g. dropped events, 
possible hot or dead pixels, parallax-caused geolocation 
errors) and communicating this information to users are 
being examined. 
 
The output of the PLT is a GLM calibration parameter file. 
The PLT could result in algorithm changes or new 
algorithms. In practice, the PLPT will overlap with the PLT. 
Some instrument-related PLTs must be completed prior to 
detection efficiency (DE) and False Alarm Rate (FAR) 
related PLPT assessments. Flexibility is required so that 
RTEP thresholds can be tentatively set, the DE/FAR tested 
using PLPT tools, then re-tuning the RTEP thresholds 
accordingly. This back-and-forth tuning process is vital for 
thoroughly optimizing the GLM. 
  
2.2. Post-Launch Product Test Phase 
 
The PLPT includes four main activities. The first is the 
Reference Data Comparisons (RDC) which determines 
whether the GLM is meeting specifications for detecting 
lightning flashes (Flash Detection Efficiency, FDE), rejecting 
false flashes (False Flash Rate, FFR), and locating the 
lightning in time and space. Reference ground-based 
lightning observation networks have been characterized and 
shown useful for GLM calibration and validation. Initial 
emphasis is placed on the well-characterized regional 
Lightning Mapping Array (LMA) networks and the National 
Lightning Detection Network (NLDN) over CONUS. 
 
The second activity is Algorithm Testing (AT) that 
determines whether the GLM algorithm is correctly filtering, 
geolocating, and clustering the raw Level 0 (L0) data, which 
contains both backgrounds and lightning. The GLM 
clustering algorithms were developed with insights gained 
from the OTD and LIS, and are validated using data from 
various ground-based reference datasets. 
 
The Instrument Navigation and Registration Testing (INRT) 
determines whether the GLM navigation is meeting 
specifications. Ground-based lightning detection networks 
also provide a baseline for this comparison, but additional 
meteorological observations are included (e.g., WSR-88D 
radar). Cases of interest are initially investigated followed by 
more in depth analysis as more data become available. 
 
The Long Term Baseline Testing (LTBT) focuses on 
determining the present GLM sensitivity, how it compares to 
the Lightning Imaging Sensor (LIS) and the Optical 
Transient Detector (OTD), and how it varies over time. The 
LTBT employs many sensors and observes patterns over 
various regions and seasons. Field campaigns are also 
designed to contribute valuable insights into the GLM 
performance capabilities.  
 
The PLPT tests each contribute to all three data levels, 
including (1) Beta – minimally validated, may still contain 
significant errors, (2) Provisional – analyses are sufficient for 
qualitative and limited quantitative determination of product 
fitness-for-purpose, and (3) Fully Validated – analyses are 
sufficient for full qualitative and quantitative determination 
of product fitness-for-purpose. With more data, better 
statistics, and more locations come more confidence in the 
GLM lightning product. 
 
 
2.3. GOES-R Field Campaign 
 
The GOES-R field campaign supports post-launch product 
validation. A ~6 week field campaign (~100 flight hours) has 
been planned with the high-altitude NASA ER-2 platform 
coordinated with ground-based and near surface observations 
(March – May 2017). During Phase 1 (2 weeks) the ER-2 
will be based in Palmdale, CA and during Phase 2 (4 weeks) 
the ER-2 will be based at Warner Robins AFB. 
 
NOAA science participates in all phases of the GOES-R 
calibration life-cycle. The GOES-R Calibration Working 
Group (CWG) has provided excellent support in the pre-
launch calibration data analysis to verify the pre-launch 
predicted instrument performance. The CWG has established 
an in-depth knowledge of the GOES-R instruments through 
extensive pre- and post-launch support. A strong 
communication line exists between the CWG and Algorithm 
Working Group (AWG). Understanding both CWG and 
AWG performance concerns and validation limitations 
fosters the successful cooperation in field campaign 
activities. 
 
The GLM field campaign focuses on validating the 70% 
flash detection efficiency and 5% false alarm rate. The 
primary objective is to provide validation of GLM flash 
detection efficiency day and night over land at well 
characterized total lightning observation sites (e.g., Northern 
AL, Lubbock TX, Norman OK, KSC FL, and 
Wallops/Washington D.C.). A secondary objective is to 
provide validation of day/night GLM flash detection 
efficiency at other land locations and over the ocean. A 
tertiary objective is to provide validation of GLM flash 
location and time stamp accuracy, as well as GLM image 
navigation and registration (INR) accuracy. 
 
The GLM field campaign validation priorities include 
collecting coincident and collocated high altitude data over 
thunderstorms with the Fly’s Eye GLM Simulator (FEGS). 
The minimum collection set includes over-flights of 
thunderstorms over total lightning super sites. Emphasis is 
on large scale convection such as Mesoscale Convective 
Systems (MCSs) from pre-storm through entire evolution 
(include all times of day and other storm types). The 
secondary collection set includes over-flights of 
thunderstorms at other locations (day/dawn or dusk/night; 
high/low latitudes; land/ocean; various storm types/regimes). 
A successful field campaign will include a sample size on 
the order of 1000 flashes for any region and period of interest 
in order to characterize detection efficiency, geolocation, and 
time-stamp accuracy.  
 
3. SUMMARY 
 
Is this necessary? 
 
4. ACKNOWLEDGEMENTS 
 
Funding for this project was provided by NOAA/NESDIS to 
the NOAA Cooperative Institute for Climate and Satellites – 
Maryland (CICS-MD) and to the NASA George C. Marshall 
Space Flight Center.  The contents of this paper are solely the 
opinions of the authors and do not constitute a statement of 
policy, decision, or position on behalf of NOAA, NASA or 
the U.S. Government. 
 
5. REFERENCES 
 
[1] Goodman S. J. et al., 2013: The GOES-R Geostationary 
Lightning Mapper (GLM). Atmos. Res., 125–126, 34–49. 
doi:10.1016/j.atmosres.2013.01.006. 
 
[2] Mach, D. M., H. J. Christian, R. J. Blakeslee, D. J. Boccipio, S. 
J. Goodman, and W. L. Boeck, 2007: Performance assessment of 
the Optical Transient Detector and Lightning Imaging Sensor, J. 
Geophys. Res., 112, D09210, doi:10.1029/2006JD007787. 
 


Characterizing the GOES-R (GOES-16) Geostationary Lightning Mapper (GLM) On-Orbit Performance

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