**National Polar-orbiting Operational Environmental Satellite System
(NPOESS) Benchmark Report for Aviation Applications**

Version 5.0

Wayne F. Feltz\* and David B. Johnson^Ø^

\*Cooperative Institute for Meteorological Satellite Studies, University
of Wisconsin--Madison

^Ø^NCAR, Research Applications Laboratory, Boulder, Colorado

**1.0 Introduction and Background**

The National Polar-Orbiting Operational Environmental Satellite System
(NPOESS) is a new satellite system intended to provide global coverage
from low-earth-orbit (LEO) in support of our military and civilian
weather agencies, providing a wealth of environmental information to
other government agencies, environmental and atmospheric scientists, and
private industry. The Integrated Program Office (IPO) representing NOAA,
NASA, and the DoD manages the NPOESS program. This benchmark report
reviews the current NPOESS program, with particular reference to its
capabilities and to the potential benefits this system can offer in
support of domestic and international aviation. The NPOESS
instrumentation most critical in supporting aviation weather include the
Visible/Infrared Imager and Radiometer Suite (VIIRS), Cross track
Infrared Sounder (CrIS), space weather sensors, and the Conical Scanning
Microwave Imager/Sounder (CMIS) and are focused on within sections 4 --
7.

The NPOESS program, inaugurated in 1994, is working to combine the DoD's
Defense Meteorological Satellite Program (DMSP) and NOAA's
Polar-orbiting Operational Environmental Satellite (POES) program into a
single system serving both of these agencies and the public at large.
The POES and DMSP programs have existed in parallel back to the earliest
days of space exploration. Both of these satellite systems consist of
polar orbiting satellites in sun-synchronous orbits at altitudes of
approximately 850 km above the earth, usually termed low-earth-orbit.

These two polar programs are complemented by a separate meteorological
satellite program managed by NOAA, making use of satellites in
geostationary orbit, 35,800 km above the equator. These satellites,
termed Geostationary Operational Environmental Satellites (GOES), rotate
at exactly the same angular rate as the earth revolves on its axis and
thus appear to be suspended at a fixed position directly over the
equator. As a result, the GOES satellites are uniquely capable of
viewing the earth from the same perspective, around the clock. Viewing
the earth on a continental scale, but with frequently updating imagery,
geostationary satellites give us the ability to closely monitor rapidly
changing conditions. The GOES satellites, however, are not able to
monitor the earth's polar regions and have a fixed, unchanging
perspective of the earth disk.

Stationed in low-earth-orbit, polar satellites, on the other hand,
circle the globe from pole to pole. They view most points on the entire
surface of the earth at least twice each day, while crossing the poles
14 times a day. Operational polar satellites are most often maintained
in sun-synchronous orbits, slightly inclined beyond a true north-south
orbital plane. This oblique orientation causes the satellite to shift
its orbital plane about one degree very day, keeping the orbit aligned
at the same relative orientation to the sun every day of the year. With
their relatively low altitude, polar satellites are well positioned to
collect high-resolution imagery and perform global observations using a
single set of observational instruments having uniform sensitivities,
calibration, and solar illumination angles.

While the DMSP and POES satellites have complex instruments with many
different observing capabilities, each system has developed its own
unique perspective and focus. For example, military satellites have
concentrated on high-resolution cloud imagery for operational support of
air and sea operations and have long used light enhancement technologies
to obtaining nighttime visible imagery. In contrast, NOAA's POES
satellites were primarily used for obtaining global, satellite-based
soundings for operational assimilation into numerical models, along with
high-resolution multi-spectral imagery of clouds, oceans, and the
earth's surface.

In the early years, NOAA's operational TIROS satellites were balanced by
NASA's Nimbus research satellites testing new technologies for transfer
to NOAA for operational use. When the Nimbus program ended, innovation
within the NOAA program slowed. The DoD's program, on the other hand,
maintained its clear focus on operational support, while maintaining a
slow but constant influx of new sensors for evaluation and testing,
distinguished by their "special sensor" designations. The DMSP program
was particularly innovative with the development of microwave
radiometers, such as the versatile SSM/I microwave imager.

With the emergence of NASA's Earth Observing System (EOS) program in the
late 1990s and increased societal concern for the environment and
climate monitoring, NASA once again began to apply new technologies to
earth observation. And, like the Nimbus satellites of an earlier era,
the new satellites and instruments pointed the way for transferring
advanced technologies to operational use. With the end of the Cold War,
there was also renewed interest in consolidating the military and
civilian polar orbiting satellite programs around advanced technologies
and combining the best of both programs into a cost effective, unified
system. programs into a cost effective, unified system.

**2.0 Convergence and Synergy**

The planned integration and convergence of the two U.S. polar systems
has proved to be difficult. The DoD and NOAA programs are quite
different, with a long history of optimization for their own
requirements.

In part reflecting current procurement strategies, and in part in an
attempt to find common ground, the specifications of the integrated
system components have been defined in terms of "environmental data
records" (EDRs) instead of specific technical criteria for each hardware
component. The EDRs, however, were formulated relatively early in the
integration process and generally reflected the traditional respective
roles of the POES and DMSP systems. Potential aviation applications
tended to be missed by the EDR identification process.

Historically, aviation weather has made intensive use of airport surface
observations and weather radars, with little emphasis on satellite
observations. In recent years, however, as a result of increasingly
attractive satellite-based observing systems and through focused efforts
like NASA's Advanced Satellite Aviation-weather Products (ASAP)
initiative, satellite measurements are gaining more prominence. In
particular, satellite observations are increasingly important over
remote oceanic and polar regions, because of the limited availability of
other observing systems and the dramatic increase in long haul flight
operations. Satellite data from both the geostationary and polar
orbiting perspectives are being used to significantly improve numerical
weather prediction models. Satellite products used within the models
include radiances, cloud location/height, and total precipitable water.

An examination of the basic features of polar orbits and coverage tends
to highlight the complementary relationship between the geostationary
and polar observing systems, while at the same time illustrating the
potential contributions of the converged polar systems.

***Orbits and Coverage:*** Figure 2.1 illustrates the orbital path and
imaging swath of an operational polar satellite and puts its coverage in
perspective to the northern-most limits for using geostationary
observations. Figure 2.2 shows the extensive overlap between successive
orbital passes of a single POES or DMSP satellite.

When viewed from an equatorial perspective, consecutive imaging swaths
of an operational polar satellite overlap, but only marginally. As you
move northward the overlap increases and a given area may be imaged by
two, or even three consecutive orbits. For the current generation of
POES satellites, however, the loss in image resolution towards the edges
of the imaging swath limits the usefulness of many of these extra
satellite passes. However, additional passes are often available to help
monitor polar regions in support of aviation. In Figure 2.2, for
example, the pass labeled #5 directly flies over Alaska, while passes #4
and 6 also view large areas of the state. While pass #7 initially seems
to be well out of view of Alaska, it eventually slides by Alaska on an
east-west pass at about 80° N, close enough to view central and northern
Alaska. Several other east-west passes will also cross over the pole
close enough to view Alaska. The essential requirement to make use of
these "extra" overpasses, is NPOESS's ability to collect high
resolution, well-calibrated imagery towards the edges of the scan swath
using the new VIIRS instrument.

Further northward, the polar orbits continue to converge, eventually
permitting direct observations of the pole from every orbital pass from
each POES, DMSP, METOP, or NPOESS satellite. With a three orbit
constellation, the average time between overpasses would be slightly
more than 30 minutes, allowing effective wind tracking, volcanic ash
plume movement, and frequent monitoring of the growth and evolution of
northern storms.

![](media/image1.png){width="5.997222222222222in"
height="4.798611111111111in"}

*Figure 2.1. An example of a sun-synchronous polar orbital track over
the North Pole. The slightly inclined orbit does not extend much further
north than 80°, but the broad imaging swath extends across the pole and
beyond. The yellow arcs indicate the traditional limit of 60° for useful
application of geostationary observations. The four arcs indicate the
limits of coverage for Meteosat, GOES-East, GOES-West, and MTSAT.*

![](media/image2.png){width="5.997916666666667in"
height="4.799305555555556in"}

*Figure 2.2. Consecutive orbits of POES or DMSP satellites show
considerable coverage overlap in the northern-most coverage areas.*

***Improved Station-keeping:*** Historically, operational POES
satellites have not been equipped with on-board propulsion systems to
maintain their equatorial crossing times or altitude and some have
drifted over four hours away from their initial crossing time during
their operational life. More recently NESDIS formulated an orbital
insertion solution to reduce the crossing time drift to less than 30
minutes over an anticipated six-year mission (National Research Council,
2000). NPOESS satellites will have improved station-keeping abilities,
with over seven years of on-board fuel for orbital station keeping to
within +/- 10 minutes of the intended equatorial nodal crossing time.

With a substantially improved station-keeping ability, the three
satellite NPOESS/METOP operational configuration could be fine-tuned to
provide uniform time intervals between successive northern-most polar
crossing times, with each of the three satellites following each other
over the pole at 34 minute intervals (with all three satellites in
carefully controlled 102 minute orbits). The essential requirement for
this coordinated orbital phasing is to adjust the equatorial crossing
times to be offset from each other by a time interval equal to two and
one-third orbits, a change of only two minutes from the nominal 4 hour
offset between equatorial crossing times envisioned for the 3-orbit
NPOESS/METOP configuration. Maintaining the uniform polar crossing time
intervals [between]{.underline} successive satellite passes would
require the satellites to have virtually identical orbital periods, but
without any special requirements for the other orbital parameters. This
same offset in the equatorial crossing times would also ensure that
successive passes by satellites carrying instruments that only scan over
a limited width swath (like CMIS or its ultimate replacement) would
collect data at all latitudes to fill in the gaps between previous
passes.

**3.0 Nunn-McCurdy Program Review Revisions**

Following a steady stream of program delays and increasing cost
estimates, the NPOESS program recently crossed a threshold designed for
Department of Defense procurements[^1] and has undergone a major review
leading to significant changes to the program. This section reviews the
current status of the modified NPOESS program, as of October 2006, with
particular reference to the potential applications of NPOESS
observations in support of aviation operations, safety, and efficiency.

The fundamental focus of the NPOESS program is to successfully integrate
the separate DMSP and POES polar meteorological satellite systems into a
single new system that will provide all the essential observational
requirements of each program while saving money by eliminating
duplication of instruments and capabilities and by reducing the total
number of satellites required for the combined missions. Integration and
consolidation of these historically separate systems has been difficult.
The very size of the new integrated program has added to the
difficulties, with proponents of each individual sensor or application
realizing that it will be a long time before the NPOESS system will be
able to be upgraded or improved. This mindset has contributed to a
general rush to design all the needed instrument improvements into the
initial NPOESS configuration, essentially updating every component of an
already complex system.

The transition from the current system with separate DMSP and POES
satellites and support facilities will be long and difficult. At the
same time, EUMETSAT (the European Meteorological Satellite Agency) has
initiated an independent series of advanced, operational polar-orbiting
meteorological satellites, termed METOP. The first satellite in this
series, METOP-A, was successfully launched on 19 October 2006. The METOP
satellites represent the first European operational satellites in polar
orbit. As part of the transition to NPOESS, the U.S. and EUMETSAT have
developed integrated plans for an Initial Joint Polar-Orbiting
Operational Satellite System (IJPS) with the METOP satellite replacing
one of the traditional NOAA POES operational satellites. The METOP
complement of instruments therefore included both new European-designed
instruments as well as legacy instruments provided by the U.S. to
duplicate current POES capabilities[^2] and maintain a consistent data
stream for operational users of the polar observations. In contrast, the
eventual NPOESS system was designed as a completely U.S. program with
U.S. satellites in all three sun-synchronous orbits, distinguished by
their equatorial crossing times.

During the transition to the NPOESS era, already contracted DMSP
satellites would continue to be launched and NASA's aging Earth
Observing Satellites (*EOS*, including *Terra, Aqua*, and *Aura*) would
continue to be used semi-operationally for some applications. The NPOESS
risk reduction satellite, NPP, would also provide quasi-operational data
sets during the transition period and assist in the early adoption of
the new sensors for critical applications that can make use of the new
systems and capabilities.

Table 3.1 summarizes the instruments originally scheduled for the three
separate NPOESS orbits. While all NPOESS satellites will use the same
bus, power, and communication hardware, the individual satellites will
customized with their own specific complement of observing systems. The
major instruments supporting operational requirements (VIIRS, CMIS,
SARSAT, and ADCS) were to be flown on all NPOESS satellites. Instruments
considered climate related, or research oriented, were generally limited
to being flown on a single orbital slot. The space environment sensor
suite (SESS) and the two critical sounding systems (CrIS and ATMS),
however, were only scheduled for inclusion on satellites in two of the
scheduled orbits. This arrangement reflects the availability of the
current generation of legacy instruments, which are only available on
the two operational POES satellites at any one time, and a clear effort
to economize on the number of instruments being contracted. However,
this strategy represents a deficiency in the original system
implementation plan. Having an instrument on all three satellite orbits
gives better coverage, faster updates, and enhanced reliability due to
the in-orbit redundancy.

The proposed changes to the NPOESS system configuration and capabilities
following the Nunn-McCurdy reassessment reflect an emphasis on
operational requirements, continuity of existing capabilities, risk
reduction, affordability, and growth potential. The starting point thus
preserves the new satellite bus and supporting space systems for power
and communication, while cutting back on less essential or climatic
instruments. Some systems experiencing development problems are being
cancelled or redesigned for less aggressive specifications to reduce
risk and cost. Climate and research sensors, with the exception of the
important total column ozone monitoring capability, are being removed
from the core program, while preserving all the system integration and
support capabilities so that they can be flown on the NPOESS satellites
if funding later becomes available.

**NPOESS Instrument Assignments, Pre-Nunn-McCurd**y

  ----------------- ----------------- ----------------- ------------------
  **AM, C3 & C6**   **MID-AM, C1,     **PM, C2 & C5**   **Comments**
                    C4**                                

  **VIIRS**         **VIIRS**         **\*VIIRS**       **Imager**

  **CrIS**                            **CrIS**          **Hyperspectral\
                                                        Souder**

  **ATMS**                            **\*ATMS**        **Microwave\
                                                        Sounder**

  **CMIS**          **CMIS**          **CMIS**          **Conical Scan\
                                                        Microwave**

  **SESS**          **SESS subset\    **SESS**          **Space Weather**
                    (C4 Only)**                         

                                      **\*OMPS\         **Ozone**
                                      (both Limb &      
                                      Nadir)**          

  **SARSAT**        **SARSAT**        **SARSAT**        **Sea/Air Rescue**

  **ADCS**          **ADCS**          **ADCS**          **Data Collection\
                                                        Services**

  **TSIS**                                              **Solar
                                                        Radiation**

                                      **ERBS**          **Earth\
                                                        Radiation
                                                        Balance**

  **ALT**                                               **Radar\
                                                        Altimeter**

                    **APS**                             **Aerosol\
                                                        Polarimetry
                                                        Sensor**

  **Previous                                            
  Satellites in                                         
  Similar Orbits**                                      

  **DMSP**          **POES, DMSP\     **POES, NPP\      **Previous
                    Terra**           Aqua**            Satellites\
                                                        in this orbital
                                                        slot**
  ----------------- ----------------- ----------------- ------------------

*Table 3.1. NPOESS Program Summary prior to the June 2006 Nunn-McCurdy
program review and revisions. With the exception of CrIS, ATMS, and
SESS, all key operational instruments, including SARSAT and ADCS, were
intended to be flown on all three orbits. Climate and research oriented
satellites were generally designated a spot on a single satellite at any
one time. Instruments to be flight tested on the NPOESS Preparatory
Project (NPP) satellite are identified by an asterisk (\*). The overall
NPOESS constellation was designed as a stand-alone system, with the
European series of METOP satellite viewed as a separate, independent,
complementary system.*

Table 3.2 summarizes the instrument assignments and overall system
configuration following the Nunn-McCurdy reassessment. Most notably, the
NPOESS lifetime program was reduced from six satellites to four, with
the elimination of the satellites for the mid-morning orbit. The
mid-morning orbital slot, however, will be filled by European METOP
satellites. The other major change was the cancellation of the
problematic CMIS instrument, with the goal of opening bids for a new,
less expensive instrument with less developmental risk (termed CMIS-lite
in the table).

**NPOESS Instrument Assignments, Post-Nunn-McCurd**y

  ----------------- ----------------- ----------------- -------------------
  **AM, C2 & C4**   **MID-AM, METOP** **PM, C1 & C3**   **Comments**

  **VIIRS**         **AVHRR/3**       **\*VIIRS**       **Imager**

                    **IASI**          **CrIS**          **Hyperspectral\
                                                        Sounder**

                    **AMSU**          **\*ATMS**        **Microwave\
                                                        Sounder**

                    **HIRS\                             **Additional
                    MHS**                               Legacy\
                                                        Sounders**

                    **GRAS**                            **GPS occultation\
                                                        soundings**

  **CMIS-Lite**     **ASCAT**         **CMIS-Lite\      **Conical Scan\
                                      (not ready for    Microwave**
                                      C1)**             

                    **SEM-2**         **SEM-2**         **SESS
                                                        replacement**

                    **GOME**          **\*OMPS          **Column Ozone**
                                      (Nadir)**         

  **SARSAT**        **SARSAT**        **SARSAT**        **Sea/Air Rescue**

  **ADCS**          **ADCS**          **ADCS**          **Data Collection**

                                                        

  **SESS**                            **SESS**          **Non-manifested\
                                                        Instruments\
                                                        (integration
                                                        possible\
                                                        with additional\
                                                        external
                                                        funding))**

  **TSIS**                            **OMPS\           
                                      (limb)**          

  **ALT**                             **ERBS**          

                                      **APS**           

  **Previous                                            
  Satellites in                                         
  Similar Orbits**                                      

  **DMSP**          **Terra\          **POES, NPP\      **Previous
                    POES, DMSP**      Aqua**            Satellites\
                                                        in this orbital
                                                        slot**
  ----------------- ----------------- ----------------- -------------------

*Table 3.2 NPOESS Program Summary following the Nunn-McCurdy program
review and revisions (status as of October 2006). The mid-morning
satellite coverage will be provided by the European METOP satellite
series (shaded in blue), with de-scoped NPOESS satellites covering the
early morning and afternoon orbits. Instruments to be flight tested on
the NPOESS Preparatory Project (NPP) satellite are identified by an
asterisk (\*). Instruments highlighted in orange have been removed from
the core NPOESS program plan, but can be integrated and flown if outside
funding will support the remaining development costs, as well as the
cost of the instrument and its support.*

Following the Nunn-McCurdy review process, all the new space environment
instruments being developed for NPOESS were descoped, and will be
replaced by the current SEM-2 instrument. From an operational civilian
aviation perspective, this change maintains most of our current
capabilities. The European METOP satellite will be used for one of the
originally proposed 3-orbit NPOESS constellation of satellites, and it
will fly the SEM-2. As an additional cost saving, however, the SEM-2
instrument will only be included on the manifest of two of the three
METOP/NPOESS operational satellites at any one time.

The most serious loss to our capability for monitoring space weather
appears to be the elimination of the electric field measurements and the
ultra-violet disk imager, which extends the direct *in situ* particle
monitoring capability of current sensors to a broader view of the
overall patterns in particle density. There is also a continuing need to
modernize and update the SEM-2 instrument and, in principle, the space
weather instruments should be a regular component on all of the
METOP/NPOESS satellites.

This CMIS instrument package has been eliminated from the proposed
NPOESS instrument suite. A less expensive and smaller risk microwave
instrument will most likely open for bids termed CMIS-lite. The
microwave sounder is crucial for global data assimilation to improve
global NWP models that are used to support aviation routes and hazard
avoidance. The microwave sensor also provides inference of oceanic wind
speed and direction, important for convective initiation nowcasting over
oceanic areas.

NPOESS sensor descriptions directly impacting aviation weather
applications will follow in sections 4-8, while deficiencies gaps, and
shortfalls will be discussed in section 9.

**4. Visible/Infrared Imager and Radiometer Suite (VIIRS)**

[]{.mark}

The VIIRS instrument will combine the capabilities of the NOAA Advanced
Very High Resolution Radiometer (AVHRR) and the Defense Meteorological
Satellite Program (DMSP) Operational Linescan System (OLS). VIIRS will
consist of 22 visible, near-visible and infrared channels (table 4.1)
between 0.3 and 14 micrometers providing global time latency reception
of 30 minutes or less, true color imagery, and consistent image
resolution from nadir to scan limbs. A comparison of the VIIRS spectral
channels versus OLS, AVHRR, MODIS, and GOES is shown in figure 4.1.

Many lessons learned from MODIS within the risk reduction process were
applied to VIIRS instrument and algorithm development. Some highlights
include:

-   VIIRS mirror reflectance will be carefully characterized as a
    function of scan angle.

-   Stray light has been reduced in VIIRS (uses rotating telescope
    instead of exposed scan mirror\... similar to SeaWIFS).

-   The cirrus detection band (1.38µm) has been narrowed spectrally to
    further reduce earth scene background illumination that should
    improve cirrus detection.

-   Destriping VIIRS imagery will leverage off of the MODIS experience.

Reduction of time latency of the VIIRS data will provide more useful
product dissemination for aviation nowcasting and forecasting.
Operationally AVHRR can provide radiance data (not products) over North
America at 30-45 minute resolution. Globally, time latency for AVHRR
imagery can be up to 90 minutes. The VIIRS data products should be
available globally in less than 30 minutes from overpass time through a
network of ground stations and fiber optics, even for forecasters
remotely located thousand of miles away (Lee et al. 2006). Currently,
the only pathway to short temporal latency for MODIS data is to have
access to a direct broadcast antenna feed that are owned primarily by
research institutions and private companies, otherwise global MODIS
coverage is available at a minimum 3-hour time latency, which make the
data unusable for most nowcasting/forecasting applications.

Nearly uniform horizontal resolution from nadir to limb will be achieved
with the VIIRS sensor. Figure 4.2 shows an example of this improvement
by comparing MODIS and VIIRS (simulated using the LANDSAT Thermatic
Mapper) at nadir and limb edge. Both MODIS and AVHRR exhibit the same
loss in resolution near the ends of their respective scan swaths. The
near constant resolution will provide much more useful information from
the imager swath than is available with current operational and research
systems. Two spatial resolutions will be available. Imaging channels
(notation with an I in Table 4.1) will have a spatial resolution of 0.38
km while moderate channels (M within Table 4.1) will have a resolution
of 0.78 km. VIIRS will have a swath width of 3000 km vs. 2800 km for
AVHRR, and 2330 km for MODIS (Lee et al. 2006). A demonstration of the
spatial resolution improvement between AVHRR and VIIRS is shown in
figure 4.3. VIIRS should offer consistent imagery interpretation across
the swath not currently available with AVHRR, or even MODIS. This
improvement should amount to more image/product utility when VIIRS
passes over large-scale volcanic ash plumes, convection, and dust
clouds, all important for aviation forecasting decision support.

VIIRS will continue the MODIS true color image legacy, important for
human interpretation of meteorological events (volcanic ash, dust,
fires, etc.) and will have positive benefits for nowcasting aviation
obscuration to pilots and terminals.

VIIRS will have improved capability to monitor cloud phase transitions,
volcanic ash, and possibly fog due to the day-night band (DNB) not
available on MODIS or other civil operational meteorological satellites.
The operational VIIRS polar orbiting sensor will provide complementary
products to the EOS MODIS imager including cloud properties, earth
radiation budget, clear-air land/water surface characterization, sea
surface temperature, ocean color, and low light visible imagery. This
capability will allow operational fog detection in parts of the world
not covered by other satellites.

Another engineering improvement is the addition of dual gain bands
(emphasized with a D within the VIIRS NADIR column in Table 4.1) that
will allow improved radiance sensing at small and large dynamic radiance
ranges. For instance, ocean color would be enhanced as the band switches
to high gain (low dynamic radiance range) while the contrast between
snow, ice and soil will be enhanced within the same band in the low gain
mode (high dynamic radiance range).

![](media/image3.png){width="6.0in" height="3.2in"}

![](media/image4.png){width="6.0in" height="3.2in"}

*Figure 4.1. Spectral coverage comparison of infrared (top) and visible
(bottom) polar and geostationary imager instrumentation.*

[]{.mark}

![](media/image5.png){width="6.178472222222222in"
height="6.374305555555556in"}

*Figure 4.2. Comparison of simulated MODIS and VIIRS images at nadir
(top) and at the edge of swath (EOS bottom). Shown is the extreme
northern Persian Gulf, including portions of Kuwait and southern Iraq,
from Lee et al, 2006).*

![](media/image6.pct)

*Figure 4.3. Figure illustrating the horizontal resolution improvement
between AVHRR and VIIRS.*

**Table 4.1 VIIRS Imagery Channels**

+---------+---------+------------+----------+------------------------+
| **Band  | **      | **VIIRS    | **MODIS  | **Primary**            |
| N       | VIIRS** | Nadir      | Nadir    |                        |
| umber** |         | Pixel Size | Pixel    | **Application**        |
|         | **Wavel | (km)**     | Size**   |                        |
|         | ength** |            |          |                        |
|         |         | **Down x   | **(km)** |                        |
|         | *       | Cross**    |          |                        |
|         | *(µm)** |            |          |                        |
+---------+---------+------------+----------+------------------------+
| M1      | 0.412   | 0.742 x    | 1.0      | Ocean Color, Aerosols  |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| M2      | 0.445   | 0.742 x    | 1.0      | Ocean Color, Aerosols  |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| M3 Blue | 0.488   | 0.742 x    | 0.5      | Ocean Color, Aerosols  |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| M4      | 0.555   | 0.742 x    | 0.5      | Ocean Color, Aerosols  |
| Green   |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| I1 Red  | 0.640   | 0.371 x    | 0.25     | Imagery, Vegetation    |
|         |         | 0.387      |          |                        |
+---------+---------+------------+----------+------------------------+
| M5      | 0.672   | 0.742 x    | 1.0      | Ocean Color, Aerosols  |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| M6      | 0.746   | 0.742 x    | 1.0      | Atmospheric Correction |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| I2      | 0.865   | 0.371 x    | 0.25     | Vegetation             |
|         |         | 0.387      |          |                        |
+---------+---------+------------+----------+------------------------+
| M7      | 0.865   | 0.742 x    | 1.0      | Ocean Color, Aerosols  |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| D       | 0.7     | 0.742 x    | N/A      | Imagery                |
| ayNight |         | 0.742      |          |                        |
+---------+---------+------------+----------+------------------------+
| M8      | 1.24    | 0.742 x    | 0.5      | Cloud Particle Size    |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| M9      | 1.38    | 0.742 x    | 1.0      | Cirrus Cloud Cover     |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| M10     | 1.61    | 0.742 x    | 0.5      | Binary Snow Map        |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| I3      | 1.61    | 0.371 x    | 0.5      | Snow Cover             |
|         |         | 0.387      |          |                        |
+---------+---------+------------+----------+------------------------+
| M11     | 2.25    | 0.742 x    | 0.5      | Clouds                 |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| M12     | 3.70    | 0.742 x    | 1.0      | Sea Surface            |
|         |         | 0.776      |          | Temperature (SST)      |
+---------+---------+------------+----------+------------------------+
| I4      | 3.74    | 0.371 x    | 1.0      | Imagery, Clouds        |
|         |         | 0.387      |          |                        |
+---------+---------+------------+----------+------------------------+
| M13     | 4.05    | 0.742 x    | 1.0      | SST, Fires             |
|         |         | 0.259 D    |          |                        |
+---------+---------+------------+----------+------------------------+
| M14     | 8.55    | 0.742 x    | 1.0      | Cloud Top Properties   |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| M15     | 10.76   | 0.742 x    | 1.0      | SST, Clouds            |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+
| I5      | 11.45   | 0.371 x    | 1.0      | Cloud Imagery          |
|         |         | 0.387      |          |                        |
+---------+---------+------------+----------+------------------------+
| M16     | 12.01   | 0.742 x    | 1.0      | SST                    |
|         |         | 0.776      |          |                        |
+---------+---------+------------+----------+------------------------+

*Table 4.1. Description of VIIRS spectral channels, after Lee et al.
2006.*

**5. Cross track Infrared Sounder (CrIS)**

An important feature of the NPOESS suite of instruments will be the
advanced, new hyperspectral infrared measurement capabilities allowing
improved vertical resolution thermodynamic profiling, trace gas
monitoring (volcanic emissions), atmospheric motion vectors (over polar
regions), monitoring of atmospheric stability, and cloud properties.

The CrIS instrument is a hyperspectral infrared interferometer, with a
spatial resolution of 14 km covering a spectral range between 16 -- 4 um
(Figure 5.1). The broadcast spectral resolution is 0.625 cm^-1^ within
the longwave band and decreases to 2.5 cm^-1^ within the shortwave band
(2155-2550 cm^-1^). This instrument will provide thermodynamic profiles,
cloud properties, and land surface temperature/emissivity globally. It
is currently scheduled to fly with VIIRS and the ATMS microwave sounder
only in the 13:30 UTC orbit. The CrIS will provide improved measurements
of temperature and moisture profiles within the atmosphere. Its heritage
and risk reduction history follows from the current operational NOAA
High Resolution Infrared Radiation Sounder (HIRS), NASA Atmospheric
Infrared Sounder (AIRS) on EOS Aqua, and EUMETSAT Infrared Atmospheric
Sounding Interferometer Radiometer (IASI) on METOP. CrIS will provide
operational continuity of improvements seen with AIRS. Figure 5.1
compares the spectral ranges of AIRS, IASI, and CrIS. Though spectral
gaps exist on AIRS and CrIS, which are not present on IASI, similar
thermodynamic retrieval capabilities are expected from all three
platforms.

The synergy of three hyperspectral sensors making multiple passes over
the high latitudes and polar regions should provide the capability of
improved temporal and vertical resolution of derived polar wind fields.
These wind fields from the MODIS imager have shown marked NWP impact on
forecasts from the polar regions to the tropics. Improved vertical
temperature and wind data for trans-oceanic flights are due to multiple
hyperspectral instrument passes in the upper latitudes. An example of
AIRS derived winds is included in Figure 5.2. The temporal resolution
with just a single instrument is 75-80 minutes, which will be improved
with the addition of CrIS and IASI in polar orbit. The sounder offers
greater vertical resolution (due to higher spectral resolution) than the
imager, but coarse spatial resolution.

![](media/image7.png){width="6.0in" height="3.2in"}

*Figure 5.1. Spectral coverage comparison IASI, CrIS, and AIRS
hyperspectral polar orbiters.*

![](media/image8.png){width="2.3986111111111112in"
height="2.4451388888888888in"}![](media/image9.png){width="3.057638888888889in"
height="3.057638888888889in"}

*Figure 5.2. An example of AIRS water vapor derived wind field at 400
hap using three consecutive AIRS overpasses.*

***Sensor Synergy***

NPOESS PM CrIS will be partnered with ATMS (Advanced Technology
Microwave Sounder) and VIIRS to provide improved atmospheric retrieval
products. ATMS will provide all weather (through cloud retrieval)
profiles of atmospheric temperature and moisture. Cloud fraction
estimates within the CrIS FOV will be provided by VIIRS allowing cloud
clearing to be performed in CrIS cloud contaminated fields of view
(FOV). This should improve utility of the CrIS data set for atmospheric
retrieval of thermodynamic profiles.

**6. The Space Environmental Center (SEC) and the NPOESS Space
Environmental Sensor Suite (SESS):**

NOAA's Space Environment Center (SEC) is responsible for monitoring the
space environment including the radiation and charged particles flux
that surround our planet, normally called space weather. This
responsibility is critical since solar flares and coronal mass ejections
can initiate a chain of events that can result in failures in our
national power grid, interfere with navigation and communication links,
and represent a radiation hazard to airline passengers and crew, as well
as many other impacts. While high energy X-ray flares cause disruptions
in communications anyplace on Earth, the charged particles tend to
follow Earth's magnetic field lines, concentrating and descending to
lower levels in the atmosphere near the poles. This path represents a
distinct hazard for aviation because of the increasing growth in the
number of long haul flights taking polar routes.

The SEC is an operational monitoring and forecasting center and depends
on a variety of different satellite resources, including the NOAA GOES
satellites in geostationary orbit, NOAA POES satellites in
sun-synchronous low-earth polar orbits, the NASA ACE (the Advanced
Composition Explorer) and SOHO (the Solar & Hemispheric Observatory)
both located at the L1 Lagrange point[^3] in deep space. The X-ray
Imager (SXI) on the GOES spacecraft monitors the solar disk for solar
flares and provides the earliest warnings of solar disruptions that
might become hazards while SOHO simultaneously watches for coronal mass
ejections moving outward from the sun. These two satellites can give us
as much as several days warning before major geomagnetic storms reach
the earth. ACE, located on the direct line between the sun and the
earth, detects charged particles already on their way towards the earth
and provides a 20-40 minute warning. In addition to its X-ray Imager,
the GOES satellite also monitors particle concentrations reaching the
earth's atmosphere, as do the POES satellites. The POES observations are
a critical component because they measure the actual flux of charged
particles that reach Earth over the polar regions and can be used to map
the most hazardous areas; these observations need to be preserved or
enhanced on NPOESS.

For the SEC, the current instruments that directly support their
operational monitoring and forecasting roles include the current version
of the Space Environment Monitor (SEM-2) being flown on the NOAA series
of civilian POES satellites. Similar particle sensors Special Sensor
Aurora Particle Sensor (SSJ-5) particles sensors, are on the DoD's DMSP
satellite. In addition to the particle sensors, the DMSP carries the
Special Sensor Ion & Electron Sensor (SSIES-3) to monitor the plasma and
electric fields, the Special Sensor Magnetometer to monitor Earth's
magnetic field, as well as the Ultra-violet Spectrographic Imager
(SSUSI) and the Special Sensor Ultraviolet Limb Imager (SSULI) that look
down at the upper atmosphere to measure electron and neutral densities
in the ionosphere. The UV sensors are new for the DMSP program but the
plans and programs are in place to use these data at SEC when they
become available.

The SEM-2 on the NOAA POES consists of two separate devices for
monitoring the charged particle flux, TED (Total Energy Detector) and
MEPED (Medium Energy Proton and Electron Detector).

***Proposed SESS Component Instruments:*** The baseline design for SESS
included five component instruments which provided updated capabilities
and a cleaner design, merging the current DMSP and POES instruments into
a unified suite of complementary sensors: the Thermal Plasma Sensor
(TPS), a combined UV-Limb/Disk Imager, and three separate charged
particle sensors --- the Low Energy Particle Sensor (LEPS), the Medium
Energy Particle Sensor (MEPS), and the High Energy Particle Sensor
(HEPS).

Acknowledgment for section 6: Rodney Viereck, NOAA Space Environmental
Center (SEC), Boulder, Colorado

**7. Advanced Technology Microwave Sounder (ATMS) and Conical Scanning
Microwave Imager/Sounder (CMIS)**

[]{.mark}

Improvement in NWP modeling forecast accuracy is very important to the
global aviation community. Jetstream location, atmospheric stability,
and cloud forecasting are all critical for short term flight planning.
Microwave radiances have been shown to have the largest satellite-based
impact on global forecast models and are crucial for improvement in data
sparse oceanic regions. Inclusion of microwave measurements have been
implicit in the NPOESS basic design and instrument payload.

ATMS is a microwave instrument that will be the primary microwave
measurement for NPOESS global NWP assimilation. It will also complement
the CrIS instrument allowing all weather temperature and moisture
profiling. The combined CrIS and ATMS suite has been christened the
acronym CrIMSS and provides heritage AMSU-A/B and MHS like capability.
The ATMS is being developed as an enhancement (and direct descendant) to
the older AMSU, which will be flown on METOP. The newly merged NPOESS
and METOP programs might well evolve with the eventual substitution of
the ATMS (once flown and proven) for the AMSU currently scheduled for
all satellites in the METOP program.

The CMIS instrument was developed through the legacy SSM/I instrument
providing improved microwave imagery and sounding information.
Unfortunately, the CMIS instrument package has been eliminated from the
proposed NPOESS instrument suite. A less expensive and smaller risk
microwave instrument will most likely open for bids termed MIS. The
microwave sounder is crucial for global data assimilation to improve
global NWP models that are used to support aviation routes and hazard
avoidance. The microwave sensor also provides inference of oceanic wind
speed and direction, important for convective initiation nowcasting over
oceanic areas.

**8. Other NPOESS Instrumentation (some not manifested)**

**Ozone Mapping Profiler Suite (OMPS) --** The OMPS is a nadir and limb
ozone-sensing instrument providing total ozone column and profiles, may
provide insight into location of high altitude turbulence (tropospheric
folding). The limb sensing capability for this instrument has been
dropped.

**Search and Rescue Satellite Aided Tracking (SARSAT) --** The SARSAT
uses NOAA satellites in low-earth and geostationary orbits to detect and
locate aviators, mariners, and land-based users in distress

**Total Solar Irradiance Sensor (TSIS, non-manifested) --** The TSIS is
a solar irradiance monitor plus a 0.2 -- 2-micron solar irradiance
monitor used for monitoring climate change. It has been cut but may be
resurrected with other funding.

**Aerosol Polarimeter Sensor (APS, non-manifested)** -- The APS is a
polarimeter used to detect aerosol presence and loading, it will be
removed from the NPOESS payload suite unless other funding can be
acquired.

**Earth Radiation Budget Sensor (ERBS, non-manifested)** - NPOESS earth
radiation budget measurements from ERBE and CERES heritage instruments
and has been cut as a climate instrument. A NASA CERES like instrument
may replace ERBS. Other ERBS systems would require additional new
resources outside the NPOESS program. []{.mark}

**Radar Altimeter (ALT, non-manifested)** -- ALT is a RADAR altimeter
similar to that used on Jason-1 that is used to measure sea surface
topography ocean surface topography to an accuracy of 4.2 cm. This
instrument has been removed from the NPOESS payload suite unless other
funding can be obtained.

**9. Deficiencies, Gaps and Shortfalls**

**[Data Availability and Latency:]{.underline}**

Polar satellites traditionally have two modes of disseminating data and
imagery: a direct, real-time transmission that can only be received by
suitably equipped stations within view of the satellite overhead, and by
high-speed play back recorded data when passing within range of a
special, high end satellite facility. For use with numerical models, the
only way to obtain full global data sets has been to wait and have the
data relayed from a suitable satellite center capable of down-linking
the recorded data. With a limited number of receiving stations there
have often been delays of up to several hours between the observations
and their availability for use.

For the NPOESS constellation of satellites a much improved data
acquisition system termed the "Safety Net" will use as many as 15
unmanned receiving stations spread around the globe, with each site
having access to high-speed international land lines for transmitting
the satellite observations to civilian and military weather centers.
Through this system it is expected that 95% of the observations will
reach the designated weather centers within 30 minutes of the data
collection. While this is a vast improvement over the current POES and
DMSP systems, it may not meet aviation requirements for rapid access.
Instead, there may be a requirement for direct read-out stations capable
of receiving the real-time data transmissions, located in sites that can
be used to generate aviation specific weather products or transmit the
observations to central aviation centers.

With the incorporation of METOP satellites into the future NPOESS
operational system, there will have to be additional attention will be
need to be paid to rapid data collection and dissemination, with the
potential for receiving stations to be equipped with separate NPOESS and
METOP receiving stations.

Aviation weather hazards evolve rapidly and will require unusually rapid
access to the observations that may not be met by the currently proposed
dissemination system.

**[Spectral Coverage:]{.underline}**

VIIRS will have some spectral limitations, such as the lack of 14.3 --
13.21 µm CO~2~ temperature absorption bands and 7.51-6.89 µm water vapor
bands. The lack of spectral coverage on VIIRS will affect some of the
derived meteorological products capable of extraction from MODIS such as
CO~2~ slicing cloud top altitude (important for accurate cloud altitude
assignment for high cirrus clouds). In addition, accurate high level
clouds heights will be hard to achieve without CO~2~ absorption
channels. The lack of water vapor bands will impact winds derived from
tracking water vapor features over the polar regions and the inference
of turbulence estimates now possible using MODIS imagery. The 7.3 µm
SO~2~ channel will also not be present, which is important for tracking
volcanic ash SO~2~ plumes.

While spectral gaps exist within the CrIS infrared spectrum compared to
IASI, they do not significantly impact aviation related applications
developed using AIRS, NAST-I, and S-HIS technologies such as volcanic
ash SO~2~ detection, water vapor imaging, and CO~2~ slicing.

**[Variable Payloads:]{.underline}**

Introducing METOP into the NPOESS constellation is logical and bodes
well for future U.S.-European cooperation. METOP, however, was designed
to complement the current generation of POES satellites and not NPOESS.
This change is likely to require an extensive series of negotiations
that may require changes in both the NPOESS and METOP instrument
configurations.

Most notably, the older technology AVHRR/3 is not a good substitute for
VIIRS. In addition, Combining METOP and NPOESS will also present
significant problems with data access, essentially requiring parallel
data acquisition and distribution systems. Even instruments that have
quite similar capabilities, such as IASI and CrIS, may well present
difficulties for assimilation at different times into a single
operational model.

Despite these problems, some benefits for METOP-NPOESS cooperation are
noted. IASI appears to be quite comparable to the CrIS hyperspectral
sounding system and having both in orbit will allow extensive testing of
each design, perhaps resulting in the adoption of one of the two designs
for both METOP and NPOESS in the later satellites to be launched.
Similarly, the AMSU on METOP may ultimately be replaced by the U.S.
ATMS, after it is validated and experiences a period of operational
testing. The European advanced scatterometer (ASCAT) will help fill in
for the cancelled CMIS instrument, particularly with its capability of
monitoring ocean wind speed and direction, until a less ambitious
replacement makes its way to the U.S. satellite system.

Finally, using the older SEM-2 on both METOP and NPOESS will provide
seamless monitoring of the space environment, but with no advancement
over current capabilities.

Other sensors eliminated from the NPOESS core program are expected to be
shifted to other NASA or DoD satellites with some cost-saving for the
NPOESS program, but will not necessarily result in any significant
reduction in the total U.S. government costs if another funding source
is found. And in one case, an existing NASA research instrument (CERES)
will fill in for the cancelled ERBS on the NPOESS C1 satellite.

**[Direct Integration of NPOESS Aviation Requirements:]{.underline}**

The aviation community was not part of the EDR process for NPOESS. This
lack of input has produced some problems with applying heritage
satellite aviation application algorithms to VIIRS. The EDR selection
process has been modified to include aviation specific components for
future sensor development such as requirements for GOES-R Advanced
Baseline Imager (ABI) (Schmit et al, 2005). It is important for the
aviation community to be represented since trans-ocean and upper
latitude aviation weather needs are highly dependent on satellite data
and NWP models initialized with satellite data. Satellite data will be
especially important when NGATS is implemented throughout CONUS.

**10. Dramatic Improvements Expected with NPOESS Deployment**

***VIIRS***

-   Consistent nadir to limb cross track resolution to allow application
    utility over a larger domain

-   Day-Night-Band providing diurnal detection of volcanic ash, cloud
    phase, fog, and convection unique to current civil (research or
    operational) imager instruments

-   True color imagery allowing rapid qualitative human interpretation
    of aviation hazards (volcanic ash plumes, convective initiation,
    fog, etc.)

-   Dual band gain bands should provide improved dynamic range detection
    over high contrast and low contrast radiance scenes

-   Improved time latency so global products are available at the major
    weather centers for model input and decision support applications in
    no more than 30 minutes.

***CrIS***

-   Provides another hyperspectral instrument to improve vertical
    resolution for globally sounding the atmosphere

-   Coupled with AIRS and IASI, improved retrieval of wind fields at
    high latitudes and volcanic ash location and heights should be
    realized

-   More continuous coverage of land-based stability and location of low
    and mid-level moisture will provide more accurate location of
    potential convective instability

**11. Potential Future Enhancements**

For aviation applications time latency and temporal/spatial resolution
drive the utility of the products for nowcasting. Any improvement of
satellite aviation weather product availability before decision support
systems should result in an increased ability to avoid aviation hazards
and economic savings. With the implementation of fiber optic data
transmission, computer processing power, and advanced relay ground
stations, potential improvement in temporal latency should be achieved
in the future.

Since most satellite applications have been developed using heritage
operational and research imagers, the addition of CO~2~ temperature and
6.7 µm water vapor bands to the VIIRS instrument is essential for many
satellite aviation applications. The CO~2~ temperature bands provide
more accurate cloud height assignments and cloud detection. The water
vapor band is essential for detecting turbulence waves and clouds.

International coordination of satellite programs is essential,
especially for polar orbiting systems to provide consistent assets for
improved instrument synergy. Polar orbiting satellites with inconsistent
spectral ranges and scanning strategies mitigate potential collaborative
measurement capabilities that may provide more value than any instrument
itself. For instance, AVHRR/3 and VIIRS are not a feasible match for
combined wind retrieval at polar regions.

When satellite programs are developing Environmental Data Requirements
(EDR), the aviation community should play a role in defining aviation
specific needs such as volcanic ash detection, icing potential,
convective initiation, and turbulence interest field detection. It is
difficult to retroactively fit mature satellite aviation application
algorithms for spectral regions not optimal for specific hazard
detection. This has just recently been recognized within the NOAA GOES-R
program, and some aviation needs are being directly addressed within the
system requirements document.

**12. Summary**

The Nunn-McCurdy Program Review has significant impact on the role of
NPOESS in aviation weather, but the new "certified" program will still
provide significantly enhanced observational resources for aviation
applications.

The number of satellite platforms has been reduced from six to four with
METOP being used at the mid-morning slot. Only a single CrIS and ATMS
instrument will be deployed. NPOESS will be particularly valuable over
northern (Alaska) and polar regions, but also useful globally. Although
several imager spectral bands are missing as compared to current
operational/research instrumentation, VIIRS will provide low-light
imaging capability, near uniform nadir to limb horizontal resolution,
and improved temporal latency. Therefore, many of the current
satellite-based aviation algorithms may have to be modified to support
the VIIRS instrument. CrIS will provide an additional hyperspectral
platform to characterize atmospheric stability and should provide
enhanced forecasting information at high latitude aviation routes where
the volcanic ash threat is significant. With the current timeline, the
first NPOESS launch is expect in FY2009. NPOESS will provide great
enhancement to observational capabilities to support aviation, and the
community is looking forward to its availability.

**13. Acknowledgment**

This benchmark report was funded by the NASA Applied Sciences Program
and the NASA Aviation Safety and Security Program through the NASA
Advanced Satellite Aviation-weather Products (ASAP) project grant number
#4400071484.

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**Acronyms**

ABI Advanced Baseline Imager

ACE Advanced Composition Explorer

ADCS Argos Data Collection System

AIRS Atmospheric InfraRed Sounder

ALT Radar Altimeter

AMSU Advanced Microwave Sounder Unit

ASAP Advanced Satellite Aviation-weather Products

ASCAT Advanced Scatterometer

ATMS Advanced Technology Microwave Sounder

AVHRR Advanced Very High Resolution Radiometer

CERES Clouds and the Earth's Radiant Energy System

CMIS Conical Scanning Microwave Imager/Sounder

CONUS Continental U. S.

CrIS Cross-track Infrared SOunder

DMSP Defense Meteorological Satellite Program

DNB Day-night band

DoD Department of Defense

EDR Environmental Data Record

EOS Earth Observing System

ERBS Earth Radiation Budget Sensor

EUMETSAT EUropean organization for the exploitation of METeorological
SATellites

FOV Field of view

GOES Geostationary Operational Environmental Satellite

GOME Global Ozone Monitoring Experiment

GRAS Global Navigation Satellite System Receiver for Atmospheric
Sounding

HEPS High Energy Particle Sensor

HIRS High-resolution Infrared Radiation Sounder

IASI Infrared Atmospheric Sounding Interferometer

IJPS Initial Joint Polar-orbiting Operational Satellite System

IPO Integrated Program Office

LEO Low earth orbit

LEPS Low Energy Particle Sensor

MEPED Medium Energy Proton and Electron Detector

MEPS Medium Energy Particle Sensor

METOP Meteorological Operational satellite Program

MHS Microwave Humidity Sounder

MODIS MODerate-resolution Imaging Spectroradiometer

MTSAT Meteorological Satellite

NASA National Aeronautics and Space Administration

NAST-I NPOESS Atmospheric Sounder Testbed-Interferometer

NESDIS National Environmental Satellite Data and Information Service

NGATS Next Generation Air Transportation System

NOAA National Oceanic and Atmospheric Administration

NPOESS National Polar-orbiting Operational Environmental Satellite
System

NPP NPOESS Preparatory Project

NWP Numerical Weather Prediction

OLS Operational Linescans System

OMPS Ozone Mapping and Profiler Suite

POES Polar-orbiting Operational Environmental Satellite

SARSAT Search and Rescue Satellite Aided Tracking

SeaWIFS Sea-viewing Wide Field-of-view Sensor

SEC Space Environment Center

SEM Space Environment Monitor

SESS Space Environment Sensor Suite

S-HIS Scanning High resolution Interferometer Sounder

SOHO Solar and Heliospheric Observatory

SSIES Special Sensor Ion and Electron Sensor

SSM/I Special Sensor Microwave/Imager

SST Sea Surface Temperature

SSULI Special Sensor Ultraviolet Limb Imager

SSUSI Special Sensor Ultraviolet Spectrographic Imager

SXI Solar X-ray Imager

TED Total Energy Detector

TIROS Television InfraRed Observation Satellite

TPS Thermal Plasma Sensor

TSIS Total Solar Irradiance Sensor

UTC Coordinated Universal Time

UV Ultraviolet

VIIRS Visible/Infrared Imager and Radiometer Suite

[^1]: Although NPOESS is a joint NOAA, DoD, and NASA program, managed by
    the Integrated Program Office, the procurement is being handled by
    the DoD and is subject to military procurement rules and procedures,
    including the Nunn-McCurdy amendment to the 1982 Defense
    Authorization Act.

[^2]: <http://www.eumetsat.int/Home/Main/What_We_Do/Satellites/EUMETSAT_Polar_System/Space_Segment/index.htm?l=en>

[^3]: See
    [**http://www.esa.int/esaSC/SEMM17XJD1E_index_0.html**](http://www.esa.int/esaSC/SEMM17XJD1E_index_0.html)