Carmen-2

The Jason-2 project is an international programme of ocean and climate study and observation. The aim of this project is to implement a global ocean observation system. Since 1992 and the TOPEX/POSEIDON and Jason-1 missions, altimetry (i.e. a precise measurement of the surface topography) has stood out as an essential tool for the study of the oceans at Earth scale.

Jason-2 has been developed in the frame of a CNES-EUMETSAT-NASA-NOAA cooperation. The satellite uses a PROTEUS platform and embarks a payload composed by a Poseidon 3 microwave radar altimeter supplied by CNES, an AMR radiometer supplied by NASA/JPL, and a triple system of precise orbitography: the DORIS instrument (CNES), a GPS receiver, and a reflector laser LRA (NASA)

Following the withdrawal of the WSOA instrument (Wide Swath Ocean Altimeter) from NASA in spring 2005, 3 new technological passengers have been allowed on board Jason-2: T2L2 and Carmen-2 from CNES, and LPT (Light Particle Telescope) from JAXA. On these two last instruments dedicated to the measure of the radiative environment, CNES and JAXA set up a cooperation through a JRE (Join Radiation Experiment).

Carmen-2 is the name given to the Carmen architecture aboard the satellite Jason-2 (MEO 1336 km, 66 °). For this mission planned initially for 5 years, Carmen-2 consists only of the ICARE-NG instrument.

CNES is the prime contractor and tasked EREMS with the ICARE-NG flight model development and manufacturing.

Because of the late Carmen-2 decision compared to the satellite planning, the instrument development was led in a very constrained calendar. The flight model has been delivered and integrated on the payload in March 2007.

Mission Objectives

Carmen-2 instrument has particular mission objectives as well as objectives related to the satellite:

• Scientific objectives: to allow the measurement of charged particles fluxes and their effects on test electronic components.
• JASON-2 associated objectives: to ensure local radiative environment characterization and the evaluation of potential drifts of the equipment in particular due to radiation from the South Atlantic Anomaly (SAA), and contribute to the instrument cross calibration in the frame of the JRE (Join Radiation Experiment).

Carmen-2 mission performances

Description and Features

The ICARE-NG/Carmen-2 instrument is composed of a data acquisition unit (SPECTRE) for the set of three radiation detectors and the component test bed (EXPERIENCE Module or MEX) identical to those of Carmen-1.

CARMEN-2 functional description

The radiation detectors are made of silicon fully depleted solid state detectors used in single and coincident mode. The SPECTRE unit performs the radiation spectrum measurement on various energy ranges. The on-board measurements consist in accumulating energy loss spectra in the junctions over a programmable accumulation period.

The reference levels of the discriminators, the gain of the amplifiers and the accumulation time are programmable and enable a possible on-board tuning optimization. The reference values are preset before launch.

In addition to the on-board acquisition, the SPECTRE unit carries out the functions of power distribution and communication interface via a 1553 bus. It also includes an interface to control one or more external instruments. In the case of the Carmen-2 mission, this capability is not used.

The objective of the EXPERIENCE module (MEX) is to measure the flight event rates and the parametric drifts of an advanced electronic component set. This module is slave to the SPECTRE unit of which it depends for power and data exchanges.

The main characteristics of the Carmen-2 instrument are the following:

Main features of the Carmen-2 instrument

ICARE-NG integrated on its panel