Next Generation Radiation Monitoring

(NGRM) A. Lupi1, P. Nieminen2, T. Watterton2, E. Jaramillo3, F. Chastellain3, U. Dose3

Within the Space Situational Awareness (SSA) programme, ESA is implementing an En-

hanced Space Weather Monitoring system, which is also making use of hosted payloads as

part of the establishment of a Distributed Space Weather Sensor System (D3S). After the

well-recognised success of SREM (Standard Radiation Environment Monitor) having em-

barked on different missions, e.g. PROBA-1, INTEGRAL, Rosetta, GIOVE-B, HERSCHEL,

PLANCK; and EMU (Environment Monitor Unit) having embarked on Galileo, ESA decided to

start the development of its successor. The SSA programme together with ESTEC, and RUAG

as leader of a European consortium (Paul Scherrer Institute-PSI, ONERA, EREMS, and IDEAS),

are realising the implementation of the first Next Generation Radiation Monitor (NGRM)

hosted by the EDRS-C satellite which will be the first hosted payload developed as part of

D3S.

[1] RHEA c/o ESA/ESOC, SSA Programme Office, [2] European Space Agency, ESA/ ESTEC, The Netherlands , [3] RUAG Space, Switzerland

NGRM is the successor of the already well-known and widely-implemented SREM and EMU units. The next generation enhances the main performance like mass, power, volume and detected

energy resolution.

It will be the first SSA-SWE unit embarked as hosted payload and the planned launch on EDRS-C will take place on October 2017.

Smaller versions of such radiation monitors have already been considered by ESA simply to ease the accommodation on different spacecraft and then match flight opportunities.

NGRM is located in the Startracker Panel West, no additional structural

bracket required to orient the NGRM towards west direction.

The unit consists of the following main subsystems:

Detector Sub System (DSS),

Stacked Detector Sub System (SDSS),

Electron Detector Sub System (EDSS),

Controller Electronics Unit (CEU),

Spacecraft Interface (SC I/F) subsystem,

Power Supply Unit (PSU).

The EDSS is made of 16 concentric ring detection diodes cov-

ered by a collimator and is used to classify electrons in one of

eight energy bins. It is optimised for the detection of electrons.

A read-out ASIC processes the signals coming from the ED.

The SDSS is composed of seven stacked diodes separated by absorbing

layers of different height. This approach allows the discrimination of the

electrons, classification of the protons in eight energy bins and the detec-

tion of heavy ions. It is optimised for the detection of protons and heavy

ions. The read-out ASIC processes the signals coming from the SD.

SC I/F implements the physical layer of the TM/TC interface. The baseline TM/TC interface is MIL-STD-1553B. Other versions such as CAN, RS-422 or SpaceWire are also available as options.

Note: The NGRM has been designed so that switching between two interface types does not require any hardware modification of the other subsystems.

CEU interfaces with all the other items. Its main goals are:

- To configure the ASICs in the DSS board, - Science data collection, - Health monitoring

- To count radiation events (protons, electrons, heavy ions), - Housekeeping acquisition - Radiation alarm

- To make the radiation acquisition histogram, - Storage for the sensor data in a SRAM - In-orbit SW patching/reconfiguration

- To support the electronics functionality (e.g. self-calibration, autonomous operation)

PSU receives +50.0 V from the primary power bus (+28.0 V as an option) and generates isolated, regulated output voltages to supply the DSS, CEU and

S/C I/F subsystems.

Electrons, 8 logarithmically-spaced channels in energy range 100 keV – 7 MeV

Protons, 8 logarithmically-spaced channels in energy range 2 MeV – 200 MeV

Heavy ions, LET from 0.1 MeV cm2/mg to 10 MeV cm2/mg

Count rates of electrons in the first 11 diodes of EDSS, normalised to the electron

beam intensity and to unity in maximum.

WHY ?

HOW ?

WHAT ?

SDSS count rate as a function of proton flux.

Blue line shows linear fit (without offset).

Power: ~2.2 W @50 V

Mass: ~1.4 kg

Size (H, W, L): 68 mm x 132 mm x 150 mm

S/C interface: MIL-STD-1553B

SpaceWire, RS-422, CAN available upon request

Operating temperature: from -40 °C to +65 °C

Count rate of events in channel SD_D0 (red) during irradiation

with 200MeV proton beam (blue).

SRAM: 2 Mbytes

Data rate depends on the settable data accumula-

tion time, also know as time resolution:

Time resolution 30 sec, data rate: 40.4 bit/sec

Time resolution 1 hour, data rate: 0.3 bit/sec

Field-of-View (FoV)

EDSS: ± 20 degrees

SDSS: ± 10 degrees