# Presentation: 194305

## EGPM

- The European Contribution to Global Precipitation Measurement

***System ******Concept***

*C.C. Lin, M. Aguirre, U. Klein, B. Rommen, P. Vogel*
*ESTEC, Noordwijk, The Netherlands*

## Artist’s View

**Artist’s View**

**Active/passive microwave sensing well established **
**Innovation: imaging + sounding + radar**

## Overall System Concept

**4****th**** Int’l GPM Planning Meeting**** ****  **Greenbelt,** **15-17 June 2004	                           **EGPM****           **3

**Overall System Concept**

## EGPM Observation Requirements

**(POD = probability of detection, FAR = false alarm rate)**
**Notes**: (*) this also includes e.g. hail; (**) this is liquid water equivalent; (***) this requires a GPM constellation

**EGPM Observation Requirements**

## Orbit Selection

**Orbit Selection**

- Sun-synchronous orbit LTDN:14:30 is complementary to other GPM satellites:
- NPOESS-1 (09:30 des.)
- NPOESS-2 (13:30 asc.)
- NPOESS-3 (05:30 des.)
- Specified orbit range was 500-675 km, but 530-590 km zone is unsuitable due to Earth resonance
- Phase A studies lead to orbit in 510-520 km range
- Coverage is function of the altitude

## Instrument Registration

- Conically scanning radiometer
- Nadir looking precipitation radar with three beams
- The 3 beams of the radar fill the central pixels of the reference 36 GHz radiometer channel

## Radiometer - I

- Five channels: 18.7, 23.8, 36.5, 89 and 150 GHz
- Dual Polarization except for 23.8 GHz
- Two sounding bands: 52.5 and 118.75 GHz, each one with 4 channels
- Antenna aperture  1 m for 510 km orbit altitude
- Rotation speed 31 rpm
- Radiometric sensitivity:
- 0.5 K for lowest frequencies
- 1 K for 89 GHz and higher
- Footprint diameter at 36.5 GHz  13.5 km
- Instrument mass  130 kg Power  110 W Data rate  62 kb/s

## Radiometer - II

## Precipitation Radar

- 35.505 GHz
- Three switched beams
- Short pulse, EIK driven
- Sensitivity:
- 	_Integration_	_Thres._	_Goal_
- 	4 km	-0.7 dBZ	1.7 dBZ
- 	2013 km2	-7.7 dBZ	-4.4 dBZ
- Vertical resolution 200 m
- Antenna diameter 1.3 m
- 4.3 km diameter footprint
- Instrument mass  55 kg Power  85 W Data rate  45 kb/s

## Satellite and Platform

**Satellite and Platform**

- Earth pointed satellite with radiometer on zenith face and radar on anti-sun face
- Configuration drivers:
- Need for radiometer fore and aft views
- Radar/Radiometer radio-frequency compatibility
- Drag reduction
- All sub-systems based on qualified technologies
- GaAs solar array fixed for drag minimization
- S and X (10Mb/s) band
- 	downlinks
- Centralized OBDH
- AOCS compensates the angular momentum of the radiometer. Unbalances and misalignments limited by manufacturing tolerances.

## Satellite Budgets and Launcher

- Satellite mass  800 kg
- Satellite power  600 W
- Satellite life of 3 years for the satellite (2 additional years for consumables)
- Pointing accuracy (3) is 2 mrad (3.5 required), co-registration is 1.55 mrad (2 required)
- 0.9 Gb per orbit, 3 Gb of memory
- Compact satellite
- Comfortable mass and adequate volume margins for launchers of the Rockot-Vega family

## Ground Segment

## Engineering Performance Radar - I

**Engineering Performance Radar**** - I**

- Radiometric performance at the top of the precipitation layer for an along-track integration distance of 4 km (single beam)

## Engineering Performance Radar - II

**Engineering Performance Radar**** - II**

- Radiometric performance at the top of the precipitation layer for 20 km  13 km integration (mission reference resolution)

## Engineering Performance Radiometer

- Performance figures obtained by standard modelling techniques
- Figures used as inputs to the end-to-end performance analysis
- All figures within requirements, but for NET (sensitivity)  at 150 GHz
- Performance fulfills mission requirements

## System Concept Summary

- Compact satellite design with a maximum science-to-cost ratio (two very similar satellite designs)
- High sensitivity radiometer and radar, optimised for observation of high latitude precipitation (low rate and solid precipitation).
- Satellite design adaptable to different LTDN
- The ground segment concept supports the needs of the various types of users: science and operational in NRT and RT, and interfaces with the GPM PPS (expected to further evolve under Earth Watch/GMES context)
- The phase A study teams under the leaderships of Astrium Ltd. and Carlo Gavazzi Space are acknowledged for their excellent design work