# Presentation: 199036

## L1 and L2 Observatories in the Post-2010 Era

- Warren Wiscombe & Jay Herman
- NASA Goddard
- Francisco Valero
- Scripps Oceanography

## 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

- IGARSS 2002

- 23 Jun

## 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.

## L1...More to Scale

- IGARSS 2002

- 23 Jun

## Simulated L1 View of Earth and Moon

- IGARSS 2002

- 23 Jun

## 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*

- IGARSS 2002

- 23 Jun

## 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!

- IGARSS 2002

- 23 Jun

## Low 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

- IGARSS 2002

- 23 Jun

## Geostationary (GEO) Satellite Views

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

- IGARSS 2002

- 23 Jun

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

- IGARSS 2002

- 23 Jun

## The Triana Satellite

**Electrostatic Analyzer /Magnetometer Boom**

**Faraday Cup**

**NISTAR**

**EPIC**

**The Triana Satellite**

- IGARSS 2002

- 23 Jun

## NISTAR: Views Whole Earth

- IGARSS 2002

- 23 Jun

## EPIC Imager:  10 channels

-  8–km resolution at nadir

- IGARSS 2002

- 23 Jun

## Triana in Launch Configuration

- IGARSS 2002

- 23 Jun

## 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

- IGARSS 2002

- 23 Jun

## L2 Earth Atmosphere Solar-Occultation Imager

- 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 Imager**

- L2–EASI

- IGARSS 2002

- 23 Jun

## Sun Eclipsed by Earth from L-2

**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 Earth**
**coordinates;**
**53,500 km on Sun**

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

- IGARSS 2002

- 23 Jun

## 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**

- IGARSS 2002

- 23 Jun

## Limb View from L2, 1.5 to 2 m

**Limb View from L2, 1.5 to 2 ********m**

- IGARSS 2002

- 23 Jun

## Other L2 Science Goals

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

- IGARSS 2002

- 23 Jun

## L1 and L2 Synergy:  Two Examples

- Day and night observations of clouds
- dynamic observations of solar disturbances outside of the bowshock and within the magnetotail

- IGARSS 2002

- 23 Jun

## 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)**

- IGARSS 2002

- 23 Jun

## Backup

- IGARSS 2002

- 23 Jun

## Halo Orbits

- 14,000 km

- 400 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

- IGARSS 2002

- 23 Jun