HESSI Science Objective Impulsive Energy Release in the Corona Acceleration of Electrons, Protons, and Ions Plasma Heating to Tens of Millions of.

HESSI Science ObjectiveHESSI Science Objective

Impulsive Energy Release in the Corona Acceleration of Electrons, Protons, and Ions Plasma Heating to Tens of Millions of degrees Energy and Particle Transport and Dissipation

To explore the basic physics ofparticle acceleration and

explosive energy release in Solar Flares

A1309.03

HESSI Non-Solar Science HESSI Non-Solar Science ObjectivesObjectives

The Crab Nebula

– Imaging spectroscopy with 2” resolution Gamma Ray Bursts and Cosmic Transient Sources

– Detected over a large fraction of the sky

– High resolution spectroscopy

– Search for cyclotron line features Steady X-ray and gamma-ray sources (point and diffuse)

– Detect by Earth occultation or through the rear grids

– Obtain high resolution spectra

– Search for line features

A1309.04

HESSI Primary ObservationsHESSI Primary Observations

Hard X-ray Images– Angular resolution as fine as 2 arcseconds– Temporal resolution as fine as 10 ms– Energy resolution of <1 keV from 3 keV to 400

keV High Resolution X-ray and Gamma-ray Spectra

– keV energy resolution– To energies as high as 15 MeV

A1309.05

Complementary ObservationsComplementary Observations

SOHO EUV images and spectra

Coronagraph images

Particle spectra and abundances

GOES Images from the Soft X-ray Imager

ACE Energetic particle spectra and abundances

TRACE UV & XUV high resolution images

CGRO X-ray and gamma-ray spectra and time histories

Ground-based Observatories

Radio and optical images and spectra

Magnetograms

A1309.06

HESSI FirstsHESSI Firsts

Hard X-Ray Imaging Spectroscopy

High Resolution Spectroscopy of Solar Gamma-Ray Lines

Hard X-Ray and Gamma-Ray Imaging above 100 keV

Imaging of Narrow Gamma-Ray Lines

High Resolution X-ray and Gamma-Ray Spectra of Cosmic Sources

Hard X-Ray Images of the Crab Nebula with 2-arcsecond Resolution

A1309.07

Relevance to Strategic PlanRelevance to Strategic Plan

Part of the Solar Connections Program - in the Roadmap for the next solar maximum.

Seeks to understand fundamental physics of solar flare energy release and particle acceleration.

Relevant to understanding relation between flares and coronal mass ejections and their effects on the Earth and its environs.

A1309.08

Expected Numbers of FlaresExpected Numbers of Flares

Microflares Tens of thousands

Hard X-ray flares with crude imaging and spectra >1000to >100 keV

Hard X-ray flares with >103 counts s-1 detector-1 Hundredsabove 20 keV allowing spatial scales to befollowed on timescales of 0.1 s

Flares sufficiently intense to allow the finest Tenspossible imaging spectroscopy

Flares with the detection of gamma-ray lines Up to 100

Flares with detailed gamma-ray line spectroscopy Tensand the location and extent of the sourcedetermined to ~40 arcseconds

HESSI Observational HESSI Observational CharacteristicsCharacteristics

Energy Range 3 keV to 15 MeV Energy Resolution ~1 keV from 3 keV to 1 MeV

Increasing to 5 keV at 15 MeV Angular Resolution 2 arcseconds to 100 keV

7 arcseconds to 400 keV

36 arcseconds to 15 MeV Temporal Resolution Tens of ms for basic image

2 s for detailed image Field of View Full Sun Effective Area - cm2 10-3 at 3 keV, 1 at 10 keV

100 at 100 keV, 50 at 10 MeV Numbers of flares ~1000 imaged to >100 keV.

~100 with spectroscopy to ~10 MeV

HESSI SummaryHESSI SummaryInstrument 9 germanium detectors (7-cm dia. x 8 cm)

Cooled to 75 K with Sunpower cooler

Grid pitches from 34 microns to 2.75 mm

1.55-m grid separation

Solar Aspect System to <1 arcsecond

Roll Angle System to 1 arcminute

Weight 120 kg

Power 110 watts

Telemetry <11 Gbits/day

Spacecraft Spinning at 12 - 20 rpm

Pointing to within 0.1° of Sun center

Launch Vehicle Pegasus XL from KSC

Orbit 38° inclination

600 km altitude, >3-year life

Launch Datemid-2000

Operations 3 yearsA1309.011

HESSI PI and Co-IsHESSI PI and Co-IsRobert Lin University of California, Berkeley PI

Brian Dennis GSFC/682 Mission ScientistCarol Crannell GSFC/682 Education & Outreach Gordon Holman GSFC/682 Flare TheoryReuven Ramaty GSFC/661 Flare TheoryTycho von Rosenvinge GSFC/661 ACE Collaboration

Patricia Bornmann NOAA GOES CollaborationRichard Canfield Montana State University Ground-based ObservationsGordon Emslie Huntsville Flare TheoryHugh Hudson Solar Physics Research Corp. ImagingGordon Hurford Caltech ImagingNorman Madden LBNL Germanium Detectors

Arnold Benz Inst. of Astronomy, Zurich, Switzerland Radio ObservationsJohn Brown Univ. of Glasgow, Scotland Flare TheoryShinzo Enome NAO, Japan Radio ObservationsTakeo Kosugi NAO, Japan ImagingFrank van Beek Delft Univ., The Netherlands Grids and ImagingNicole Vilmer Observatoire de Paris, Meudon, France Data AnalysisAlex Zehnder Paul Scherrer Inst. Switzerland Telescope design

and fabrication

A1309.012

HESSI Prime ResponsibilitiesHESSI Prime Responsibilities

UC Berkeley Germanium detectors & electronics

I & T

Ground station, MOC/SOC

Data Analysis

GSFC Grid characterization & testing

Cooler, cryostat design

Data analysis, distribution, and archiving

PSI (Switzerland) Telescope & aspect system

Thermo Electron Tecomet Finest grids (#1 - 4)

van Beek (The Netherlands) Coarser grids (#5 - 9) & mounts

Spectrum Astro Spacecraft

A1309.013

GSFC InvolvementGSFC InvolvementScience

Dennis (682) Mission Scientist

Hurford (Caltech) Imaging Scientist

Holman (682), Ramaty (661) Solar flare physics

von Rosenvinge (661) ACE/HESSI coordination

Crannell (682) Education & Public Outreach

Imaging

Clark (547), Amato (544) Grid environmental testing

Orwig (682), Lang (CUA),

Uribe (Raytheon ITSS) Optical & X-ray grid characterization

Schmahl (UMd) Image reconstruction

Spectrometer

Boyle (713) Cryostat design, cooler evaluation

Provide flight-qualified Sunpower cooler

Schwartz (Raytheon ITSS) Spectral deconvolution

Data Analysis

Gurman (682), Zarro (ARC) Solar Data Analysis Center

Tolbert (Raytheon ITSS) Data archiving and distribution

A1309.014

HESSI Imaging ParametersHESSI Imaging Parameters

Test Fine GridsTest Fine Grids

A1309.015

Tecomet Grid #1

Material: MolybdenumPitch: 34 micronsSlit width: 15 micronsTotal thickness: 1.2 mmLayer thickness: 15 micronsNo. of layers: 75Active area: 9 cm diameterAspect ratio: >50:1

• Second of two identical grids fabricated by Thermo Electron Tecomet in Woburn, MA.

• Finest, high-aspect-ratio X-ray collimator ever made.

• Provides modulation to X-ray energies in excess of 100 keV.

• Allows imaging on HESSI with an angular resolution of 2 arcseconds.

• Picture shows circular active area with fiducial and mounting features in the integral rim.

• Direction of slits is revealed by the white bar at 45º resulting from light transmitted from below through the ~1º opening angle of each slit.

Tecomet Grid #1

HESSI Top Grid TrayHESSI Top Grid Tray

Tecometgrid

van Beek grid

Aspect systemlens

Germanium DetectorGermanium Detector

A1309.019

Sunpower M77 Stirling-Cycle CoolerSunpower M77 Stirling-Cycle Cooler

Instrument SensitivityInstrument Sensitivity

Angular Coverage vs. Photon EnergyAngular Coverage vs. Photon Energy

Relative Modulation AmplitudeRelative Modulation Amplitudevs. Photon Energyvs. Photon Energy

Composite Flare SpectrumComposite Flare Spectrum

Energy Resolution vs. Photon Energy Resolution vs. Photon EnergyEnergy

A1309.024

Count Rates in Each Detector for Count Rates in Each Detector for One RotationOne Rotation

A1309.025

Prelaunch Twist Monitoring Prelaunch Twist Monitoring System (TMS)System (TMS)

A1309.026