AOS-PMM (Atmosphere Observing System - Precipitation Measuring Mission)

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Overview

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Summary

Mission Capabilities

AOS-PMM will join the AOS Constellation, which consists of AOS-Storm, AOS-Sky, and HAWCSat.

The mission carries JAXA’s Ku-Band Doppler Radar and the CNES Atmospheric Sounder Intertropical Humidity Profiles by Radiometry - New Generation (SAPHIR-NG). The JAXA Ku-Band Doppler Radar performs precipitation profiling and mapping of the atmosphere with nadir Doppler observations. These provide insights into convective dynamics, and in how precipitation forms and evolves in the atmosphere. SAPHIR-NG is a pair of high-frequency passive microwave radiometers that will make time-difference observations of ice water path and vertical ice mass flux. This instrument aims to aid our understanding of the dynamics of ice in the atmosphere, including how its formation and movement provide information on the weather and climate.

Performance Specifications

The mission’s Ku-Band Doppler Radar has a horizontal resolution of 5 km, and vertical resolutions of 250 m off nadir, and 500 m at nadir. The radar has a swath width of 255 km and operates at a frequency of 13.6 GHz.

SAPHIR-NG has a swath of 750 km with a 10 km resolution at 89 GHz, a 5 km resolution at 183 GHz, and a 3 km resolution at 325 GHz. The 89 GHz waveband has one channel, the 183 GHz waveband has six channels, and the 325 GHz waveband has three channels.

AOS-PMM will operate in a non-Sun-synchronous orbit at an altitude of 430 km with an inclination of 55°.  

Overview

NASA, in partnership with JAXA (Japanese Aerospace Exploration Agency) and CNES (National Space Center of France), is developing AOS-PMM (Atmosphere Observing System - Precipitation Measuring Mission), a satellite that will work in tandem with three other satellites in NASA’s AOS (Atmosphere Observing System) Constellation: AOS-Storm, AOS-Sky, and HAWCSat. AOS succeeds the ACCP (Aerosols, Clouds, Convection and Precipitation) Study to allow for further study into the aerosol and cloud processes that cause extreme weather and drive climate change. 1)

AOS-PMM will provide measurements of precipitation and estimates of convective dynamics based on Doppler shift provided by JAXA’s Ku-Band Doppler Radar. Insights derived from these dynamics include coupled storm dynamics and microphysics, investigations into the importance of the diurnal cycle, and the properties of high clouds in the atmosphere. AOS-PMM will work in tandem with AOS-Storm to provide time-rate-of-change information about ice production and vertical mass flux in the atmosphere utilising SAPHIR-NG (Atmospheric Sounder Intertropical Humidity Profiles by Radiometry - Next Generation), an instrument under development by CNES. 2)

AOS-PMM has a planned nominal mission life of five years.

Launch

AOS-PMM will be deployed into a non-sun-synchronous orbit at an altitude of 430 km with an inclination of 55°.

Mission Status

• July 2024: The AOS mission entered Phase B, the preliminary design and technology completion phase. 5)
• January 2023: AOS entered Phase A of its development.
• August 2022: An independent review board study was carried out to review the current plans of the mission.
• May 2022: AOS passed its mission concept review.
• May 2021: The Aerosols, Cloud, Convection and Precipitation (ACCP) Study was completed, and the planned constellation became the Atmosphere Observing System (AOS).

Sensor Complement

JAXA Ku-Band Doppler Radar

The JAXA Ku-Band Doppler Radar is currently under development for the use of cloud profiling and rain radar. It utilises cross-track scanning with a swath of 255 km and a horizontal resolution of 5 km. The vertical resolution for Doppler (nadir) and high-density (near nadir) modes is 500 m, and for nominal mode (off nadir) the vertical resolution is 250 m. The microwave waveband is set to 13.6 GHz (Ku–band). 3)

SAPHIR-NG (Atmospheric Sounder Intertropical Humidity Profiles by Radiometry - New Generation)

SAPHIR-NG is a multispectral radiometer being developed by CNES to provide time-differenced measurements of ice water path and vertical mass flux. The instrument operates across three wavebands and has a 750 km swath width. 4)

The measurements from SAPHIR-NG  will provide humidity profiles and also hydrometeor profiles under convective conditions. The benefit of having the 325 GHz band is that it can provide information about smaller scales within convective systems due to the higher spatial resolution. This instrument is designed to perform cross-track scanning with a scan angle of +/- 43°, but the 183 GHz and 325 GHz bands cause an issue of requiring distinct ground sampling grids for the two frequencies. To fully exploit the detailed hydrometeor information available at 183 GHz and the high spatial resolution available at 325 GHz, it is necessary to perform continuous measurements at 325 GHz in the along-track direction. This approach provides both high-quality information about atmospheric particles and finely detailed images of the atmosphere. 6)

Ground Segment

The planned sites for the ground segment include Fairbanks in Alaska US, Punta Arenas in Chile, Svalbard in Norway, Wallops in Virginia US, White Sands in New Mexico US, and finally GSFC (Goddard Space Flight Centre) in Maryland US. Fairbanks, Punta Arenas, Svalbard, and Wallops serve as the main telemetry and command centres, as well as the primary locations for science data downlink, each handling approximately eight contacts per day at a data rate of 4.8 Gbps. As the mission is still in the planning phase, there is potential for the inclined spacecraft to utilise Starlink communications at a rate of 1 Gbps. White Sands will serve as an augmented data downlink centre to reduce latency, and GSFC will act as the primary mission operation centre. 1)

References  

1) “Mission Overview.” NASA AOS, NASA, URL: https://aos.gsfc.nasa.gov/mission.htm

2) Symbios. “AOS-PMM Satellite Mission Summary.” CEOS Database, ESA, URL: https://aos.gsfc.nasa.gov/mission.htm

3) Symbios. “JAXA Ku-Band Doppler Radar.” CEOS Database, ESA, URL: https://database.eohandbook.com/database/instrumentsummary.aspx?instrumentID=2093

4) Symbios. “SAPHIR-NG.” CEOS Database, ESA, URL: https://database.eohandbook.com/database/instrumentsummary.aspx?instrumentID=2092

5) “Atmosphere Observing System (AOS): Science Status.” NASA AOS, 17 May 2023, URL: https://aos.gsfc.nasa.gov/timeline.htm

6) Puech, J., et al. “SAPHIR-NG HIGH RESOLUTION MICROWAVE SOUNDER: TOWARDS AN ENHANCED OBSERVATION OF THE ATMOSPHERE.” IEEE Xplore, 12 October 2021, URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9554426.