(UK)and Universita diTorino (Italy).

The visibility and connectivity created by the SOHO Data Archivehasallowed more

scientific data to be distributed in a shorter time than any previousscientific mission.

Instrumentand SpacecraftStatusAllofthe instrumentson SOHOand the spacecraftitself arein excellentcondition and

engineering evaluationsindicate they willcontinue to operate for atleastthe nextfive years. The ESA Solar System Working

GroupandtheESAScienceProgrammeCommitteehaveboth advisedESAmanagementthatSOHOoperationshouldbe

continued for an additional5 years. The purpose of this proposalisa parallelrecommendation to NASA management.

Proposal OrganizationThis proposal is divided into sevenmajor parts - SOHO Science; Operations, Data Access, and Educa-

tion/Outreach;Plansfor the SOHO Solar Maximum Scienceprogram,Implementation of the SOHO Solar MaximumScience

program,a Summary of Scientific Impact,and Programmatics.In theSOHO Science section,we describehow theSOHO

instruments function as a system, the principal results of the first year of operation, and a sample solar event followed from the

Sun to the Earth through the operation of the ISTP instrument set.In the Operations subsection, we describe the labor-intensive

but scientifically rewarding science operations process, including the ways in which we involve the larger community in SOHO

observations and data analysis. In the Data Access and Education/Outreach sections, we detail how both qualified investigators

and the general public are able to use SOHO data. In the Plans for the SOHO Solar Maximum Science program section, a basic

set of measurements used to characterize the dynamic Sun is defined and science plansfor the rise to maximum and the period

following maximum are presented. A brief Implementation plan describes how we will save development costs by achieving the

Solar Maximum Science program goals with existing capabilities. In the Scientific Impact Section, we summarize some of the

most interesting resultsfromthe mission so far,and whatwe hope to achieve in the SOHO Solar Maximum Science program.

Finally, in the Programmaticssection,we describethecurrentbudgetandthatrequired forthe"minimumviable"science

program.

III) SOHO Science

1. The Solar Interior and Solar Surface

The three interiorand surface instrumentson SOHO areGOLF,VIRGO,and MDI,allof which measurepropertiesof the

solar interior viathe techniquesof helioseismology. GOLFmeasuresthe netvelocity fluctuationsof theentire Sun,VIRGO

measures the intensity variations of the Sun in a dozen zones, while MDI makes maps of the entire surface in velocity, intensity,

and magnetic field on a grid of 1024 x 1024 points.The GOLF and VIRGO instruments are designed to achieve high absolute

precision in velocity and intensity respectively in order to detect theg-modes. The results from VIRGO are used to calibrate the

MDI measurements,while MDI mapsof magnetic field and surfaceintensity are necessary for the interpretation of the GOLF

and VIRGO frequencies and VIRGO radiometry. In addition VIRGO makeshigh precision measurements of the surface irradi-

ance.

GOLF, VIRGO, and MDI all operate continuouslyin gathering their basic data sets.In addition MDI takes data optimized for

coordinated observationswith the other SOHO experiments.In particular MDI followsthe generation and evolution of mag-

netic fieldson the granulation to globalscale with a spatialand time resolution sufficientto, for the firsttime,follow the life-

cycleof magnetic fields.MDI also providesmeasurementsof relative brightnessof active and quietregionsto enable better

understanding of the radiative flux balance data obtained by VIRGO and the behavior of the outer atmosphere followed by CDS,

SUMER, EIT, UVCS, and LASCO. It also provides direct measurements of surface motions from meso-granulation through to

global scales.

Continuousobservationsare necessaryfor some of the primary helioseismology objectives.There aretwo fundamentalrea-

sonsfor this.The first,isthattheg-mode signal,if presentin thesurfaceoscillation,hasa submillimeter amplitude in the

individual modes.Toobtain the signal to noise ratio necessary to detect such low amplitude patterns requires long uninterrupted