3 L-2 Lagrange Points L1 and L2: New Planets! L-1 At L1 and L2, the sum of the Earth’s and Sun’s gravitational fields gives a net gravitational pull equal to that at Earth. Therefore, a spacecraft at L1 or L2 must orbit the Sun with the same period as the Earth.
23 JunIGARSS L1...More to Scale
23 JunIGARSS Simulated L1 View of Earth and Moon
23 JunIGARSS L1 and L2 Observatories as Nerve Centers of the SensorWeb “Perhaps Triana’s most important contribution to Earth science observations is the potential for using L1 observations of Earth to integrate data from multiple spaceborne as well as surface and airborne observation platforms in a self-consistent global database for study of the planet and documenting the extent of regional and global change.” National Academy of Sciences report on Triana, March 2000
23 JunIGARSS Unique L1/L2 Attributes Relate and connect all other observational assets Synoptic view (all times at once) High time resolution (1 min or better) Sunrise to sunset coverage Stably pull out small, delicate effects over many years – Monthly Moon calibration opportunities – Looong integrations for higher accuracy Assist field programs Much simpler data processing compared to LEO, GEO A true global change observing location!
23 JunIGARSS Low Earth Orbit (LEO) and L1 Views 45-min LEO swath LEO view of Earth takes ~45 min to paint one swath covering ~1/14 th of the planet — 11 hr to paint whole planet. From L1, can do same in less than 1 min (over 600x faster). Sunrise to sunset instantly
23 JunIGARSS Geostationary (GEO) Satellite Views Each GEO takes min to paint its covered area.
23 JunIGARSS Spatio-Temporal Domain of a LEO Satellite vs. an L-1 Observatory L1 DOMAIN LEO DOMAIN
23 JunIGARSS Electrostatic Analyzer /Magnetometer Boom Faraday Cup NISTAR EPIC The Triana Satellite
23 JunIGARSS NISTAR: Views Whole Earth
23 JunIGARSS EPIC Imager: 10 channels 8–km resolution at nadir
23 JunIGARSS Triana in Launch Configuration
23 JunIGARSS EPIC Science Objectives Ozone Aerosols Cloud phase (ice, water) and particle shape Column water vapor UV at the surface Stratospheric dynamics “Hotspot” — vegetation direct backscatter
23 JunIGARSS Solar Occultation from Lagrange point L2 using Fourier Transform Imaging Spectrometer with 10 Meter telescope Wavelength Range: 1 – 4 m Resolution: 5 cm -1 or better Spatial Resolution: 1–2 km in altitude Available Solar Flux ~ % of Total Sun L2 Earth Atmosphere Solar-Occultation Imager L2–EASI Sun
23 JunIGARSS Detector rotates around Earth limb – 2 km altitude resolution – 1 to 4 m spectrum Exposed Sun: – 15% of solar area – 4% of solar radius Nightside Earth 440 km in Earth coordinates; 53,500 km on Sun Sun Eclipsed by Earth from L-2
23 JunIGARSS L2–EASI: Science Goals Measure greenhouse gases at sunrise, sunset... –CO 2, CH 4, H 2 O, O 3, O 2, N 2 O and get their first 3-D Mapping with resolution –Height, 2 km: Latitude, 1 o Longitude, 2 o
23 JunIGARSS L1 and L2 Synergy: Two Examples (1)Day and night observations of clouds (2)dynamic observations of solar disturbances outside of the bowshock and within the magnetotail L1 L2
23 JunIGARSS Technical Challenges at L1 and L2 Large apertures (10 meter) Communications back to Earth (at all!) Data rate back to Earth Orbit design Power at L2 Rotation of Earth Thermal control (L2)
23 JunIGARSS Backup
23 JunIGARSS ,000 km14,000 km400 km Halo Orbits can have any radius (more fuel to insert into tighter orbit)... but period is always 6 months. orbits are 3D; planar projections are Lissajous figures (orbit evolves from one quasi-ellipse to another over several years) stationkeeping once/month or more