ISCEA (INFRARED SMALLSAT FOR CLUSTER EVOLUTION ASTROPHYSICS) WILL SIGNIFICANTLY ADVANCE OUR UNDERSTANDING OF GALAXY EVOLUTION THROUGH OBSERVATIONS OF GALAXY CLUSTERS AND THE COSMIC WEB. THE ISCEA SCIENCE OBJECTIVES ARE: (1) STUDY GALAXY EVOLUTION IN DENSE ENVIRONMENTS AT REDSHIFTS 1.6<Z<2.4. (2) MAP THE COSMIC WEB ENVIRONMENT AROUND CLUSTERS AT THIS CRITICAL EPOCH. TO MEET ITS SCIENCE OBJECTIVES ISCEA WILL CONDUCT A COMPLETE CENSUS OF THE STAR FORMATION ACTIVITY IN A LARGE MASS-LIMITED SAMPLE OF THE EARLIEST THERMALIZED GALAXY CLUSTERS FROM THE ONGOING 3RD GENERATION 2 500 SQ DEG SURVEY WITH THE SOUTH POLE TELESCOPE (SPT-3G). ISCEA WILL MAP THE 3D DISTRIBUTION OF GALAXIES DOWN TO A STAR FORMATION RATE (SFR) LIMIT OF 5 SOLAR MASSES PER YEAR OUT TO RADII OF 10 MPC FOR ALL THE CLUSTERS MORE MASSIVE THAN 10^14 SOLAR MASSES FROM SPT-3G AT 1.6<Z<2.4 AND PROBE THE COSMIC WEB STRUCTURE SURROUNDING EACH CLUSTER AS TRACED BY EMISSION LINE GALAXIES (ELGS). THE ISCEA DATA WILL SPAN A WIDE VARIETY OF ENVIRONMENTS FROM CROWDED CLUSTER CORES TO THEIR VIRIAL RADII AND BEYOND MAPPING THE COSMIC WEB SURROUNDING EACH CLUSTER DIRECTLY TYING THE DENSE NODES TO THE SURROUNDING FILAMENTS. THESE OBSERVATIONS WILL PERMIT A DETAILED STUDY OF THE STAR FORMATION ACTIVITY AS FUNCTIONS OF CLUSTER MASS RADIUS AND ENVIRONMENTAL DENSITY OVER THE KEY GYR IN WHICH CLUSTERS COALESCE OUT OF THE COSMIC WEB. IN ADDITION ISCEA WILL ENABLE CLUSTER DYNAMICAL STUDIES INCLUDING VELOCITY DISPERSIONS AND PHASE-SPACE DIAGRAMS THAT CAN CONSTRAIN THE INFALL HISTORY AND MEASURE CAUSTIC-BASED MASSES. ISCEA IS A SMALL SATELLITE WITH A 25CM APERTURE TELESCOPE WITH A FIELD OF VIEW (FOV) OF 0.32 SQ DEG AND A SPECTROGRAPH WITH A DIGITAL MICRO-MIRROR DEVICE (DMD) AS ITS PROGRAMMABLE SLIT MASK. USING THE APPROACH PIONEERED BY THE DMD-BASED INFRARED MULTI-OBJECT SPECTROGRAPH (IRMOS) ON KITT PEAK ISCEA WILL OBTAIN SPECTRA OF ~500 GALAXIES SIMULTANEOUSLY AT A RESOLVING POWER OF R=?/??=1000 WITH 2.8 2.8 SLITS OVER THE WAVELENGTH RANGE OF 0.9 TO 1.7 M (EXTENSION TO 2 M TO BE STUDIED) A REGIME NOT ACCESSIBLE FROM THE GROUND WITHOUT LARGE GAPS IN COVERAGE. ISCEA WILL ACHIEVE A POINTING ACCURACY OF 2 OVER 1000 SEC BUILDING UPON THE SUCCESS OF THE PIEZOELECTRIC CONTROL STAGE AND TECHNIQUE DEMONSTRATED BY THE 6U CUBESAT ASTERIA. THIS WILL ENABLE DEEP SPECTROSCOPY OF HUNDREDS OF CLUSTER GALAXIES OVER A WIDE FOV. ISCEA WILL BE LAUNCHED AS A SECONDARY PAYLOAD MICROSAT. IT HAS A LOW EARTH ORBIT (LEO) AND A PRIME MISSION OF 2 YEARS. GIVEN THE UNIQUE CAPABILITY OF ISCEA FOR MULTI-SLIT SPECTROSCOPY IN CROWDED FIELDS WE EXPECT ISCEA TO HAVE A VIGOROUS ASTROPHYSICS GUEST OBSERVER PROGRAM IN ITS EXTENDED MISSION. ISCEA ADVANCES NASA ASTROPHYSICS OBJECTIVE TO DISCOVER HOW THE UNIVERSE WORKS AND EXPLORE HOW IT BEGAN AND EVOLVED BY ANSWERING CRITICAL QUESTIONS ABOUT HOW GALAXY CLUSTERS FORM FROM THE COSMIC WEB. THE ISCEA MISSION WILL ALSO DEMONSTRATE A KEY TECHNOLOGY THAT WILL BE AVAILABLE TO FUTURE SATELLITE MISSIONS: DMDS WILL OPEN UP A NEW WINDOW IN SPECTRSOCOPY FROM SPACE THAT ENABLES REVOLUTIONARY ADVANCES IN ASTROPHYSICS. THE ISCEA CONCEPT STUDY WILL FOCUS ON VERIFICATION OF THE FLOW-DOWN FROM THE SCIENCE OBJECTIVES TO THE SCIENCE REQUIREMENTS AND ULTIMATELY TO THE TECHNICAL REQUIREMENTS. THE DETAILED MISSION DESIGN WILL INCLUDE QUANTITATIVE MODELING OF SPACECRAFT JITTER AND FOCAL PLANE POINTING CONTROL VIA STAR-TRACKING AND TRADE-OFFS THAT IMPACT FEASIBILITY AND SCIENCE PERFORMANCE. THE ISCEA SCIENCE INVESTIGATION WILL FOCUS ON THE QUANTITATIVE MODELING OF THE TARGET SELECTION REALISTIC SIMULATIONS OF THE OBSERVED SPECTRA AND STRATEGIES FOR MAXIMIZING THE SCIENCE RETURN. THE ISCEA DESIGN STUDY WILL HAVE ACTIVE PARTICIPATION FROM THE JET PROPULSION LABORATORY AND THE ISCEA INDUSTRY PARTNERS: BLUE CANYON TECHNOLOGIES (SPACECRAFT BUS) SIGMA SPACE CORPORATION (TELESCOPE) AND BALL AEROSPACE&TECHNOLOGIES (INTEGRATION AND TEST).