L1 and L2 Observatories in the Post-2010 Era Warren Wiscombe & Jay Herman NASA Goddard Francisco Valero Scripps Oceanography.

L1 and L2 Observatories in the Post-2010 Era

L1 and L2 Observatories in the Post-2010 Era

Warren Wiscombe & Jay HermanNASA Goddard

Francisco ValeroScripps Oceanography

23 Jun IGARSS 2002 2

Multiple Vantage Points(from NASA’s Earth Science Vision)

Multiple Vantage Points(from NASA’s Earth Science Vision)

L1 Observatories

Molniya Orbit

GEO

L2 Observatories

Polesitter

balloons

3

L-2

Lagrange Points L1 and L2: New Planets!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 Jun IGARSS 2002 4

L1...More to ScaleL1...More to Scale

23 Jun IGARSS 2002 5

Simulated L1 View of Earth and MoonSimulated L1 View of Earth and Moon

23 Jun IGARSS 2002 6

L1 and L2 Observatories as Nerve Centers of the SensorWeb

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 Jun IGARSS 2002 7

Unique L1/L2 AttributesUnique 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 Jun IGARSS 2002 8

Low Earth Orbit (LEO) and L1 ViewsLow Earth Orbit (LEO) and L1 Views

45-min LEO swath

LEO view of Earth takes ~45 min to paint one swath covering ~1/14th 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 Jun IGARSS 2002 9

Geostationary (GEO) Satellite ViewsGeostationary (GEO) Satellite Views

Each GEO takes 15-30 min to paint its covered area.

23 Jun IGARSS 2002 10

Spatio-Temporal Domain of a LEO Satellite vs. an L-1 Observatory

Spatio-Temporal Domain of a LEO Satellite vs. an L-1 Observatory

L1 DOMAIN

LEO DOMAIN

23 Jun IGARSS 2002 11

Electrostatic Analyzer /Magnetometer Boom

Faraday CupNISTAR

EPIC

The Triana SatelliteThe Triana Satellite

23 Jun IGARSS 2002 12

NISTAR: Views Whole EarthNISTAR: Views Whole Earth

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EPIC Imager: 10 channelsEPIC Imager: 10 channels

8–km resolution at nadir

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Triana in Launch ConfigurationTriana in Launch Configuration

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EPIC Science ObjectivesEPIC 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 Jun IGARSS 2002 16

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 ~ 12 - 15% of Total Sun

L2 Earth Atmosphere Solar-Occultation ImagerL2 Earth Atmosphere Solar-Occultation Imager

L2–EASISun

23 Jun IGARSS 2002 17

Detector rotates around Earth limb– 2 km altitude resolution– 1 to 4 m spectrum

Exposed Sun: – 15% of solar area – 4% of solar radius

NightsideEarth

440 km in Earthcoordinates;53,500 km on Sun

Sun Eclipsed by Earth from L-2Sun Eclipsed by Earth from L-2

23 Jun IGARSS 2002 18

L2–EASI: Science GoalsL2–EASI: Science Goals

• Measure greenhouse gases at sunrise, sunset...

– CO2, CH4, H2O, O3, O2, N2O

• and get their first 3-D Mapping with resolution

– Height, 2 km: Latitude, 1o Longitude, 2o

23 Jun IGARSS 2002 19

Limb View from L2, 1.5 to 2 mLimb View from L2, 1.5 to 2 m

23 Jun IGARSS 2002 20

Other L2 Science GoalsOther L2 Science Goals

• Magnetotail• Cosmic rays• Lightning• Aurora• Airglow• Incoming bolides

23 Jun IGARSS 2002 21

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 Jun IGARSS 2002 22

Technical Challenges at L1 and L2Technical 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 Jun IGARSS 2002 23

BackupBackup

23 Jun IGARSS 2002 24

26,000 km 14,000 km 400 km

Halo OrbitsHalo Orbitscan have anyradius (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