Earth observation from the Moon

Transcription

1 Earth observation from the Moon 9th ILEWG International Conference on Exploration and utilization of the Moon Sorrento, October 2007 Vojko Bratina CNR-, L.go Fermi 6, Firenze & EARTH OBSERVATION FROM THE MOON WORKING GROUP

2 Italian Vision for Moon Exploration ASI (Italian Space Agency) funded program based on 16 studies: 3 scientific studies: In situ sensing Observation of the Universe from the Moon Observation of the Earth from the Moon Identification of scientific objectives, priority list, needed requirements 13 technological studies: Support robotics (2) Launch Vehicle study Orbital transfer module MDL (Moon Descent and Landing) (2) MW remote sensing of the Moon and from the Moon Lunar Orbiter HE (X, Gamma, neutrinos) remote sensing Lunar Lander In situ sensing instrumentation (2) HMLV (High Mobility Lunar Vehicle) Technical solutions to proposed requirements

3 1) A telescope placed at any location on the near side of the Moon can observe the entire disk of Earth: LEO: no satellite can do this. Why the Moon I 2) A satellite in geosynchronous orbit observes one third of the total area, but is limited to the same view at all times. 3) A satellite at the unstable Lagrange point between Earth and Sun (L1) only sees the sunlit side of Earth and cannot be permanent because of the need for continuous orbital corrections. L1 is about a million miles from Earth. The Earth-Moon distance is some-what less than one fourth of L1 value. 4) From the Moon, over the course of a day all sublunar points are visible. During the course of a month the entire Earth is visible, including the two polar regions. Over the course of a year the view of Earth varies in an interesting way as the Sun illuminates the Earth from different angles, consistent with the 23.5 degree tilt of the axis. Several reasons make the Moon an ideal location for long-term monitoring of the Earth. the varying views of Earth the visibility of the entire disk the relatively rapid rotation of Earth the stability of the lunar surface

4 Case study I: volcanic eruptions large explosive volcanic eruptions or large wildland fires have a devastating impact. Why the Moon II Detection of the progress of these hazards from space and monitoring their energy fluxes into the atmosphere has been a key facet to several missions for many years. The ability to do this from a lunar-based Earth observatory challenging, but beneficial. Case study II: space weather activity The atmosphere-less surface of the Moon === unique, & stable platform for VIS & UV/EUV imaging instruments improve our understanding and ability to predict space weather activity, flares, CMEs and Solar Particle Events (SPEs). Observations from the Moon can significantly improve understanding and prediction of CMErelated space weather, critical for safeguarding both robotic and human activity on the Moon and beyond.

5 Why the Moon III Case study III: atmosphere observation TIR remote sensing from the lunar surface could be potentially useful for thermal monitoring & atmospheric compositional mapping design and implementation of instrumentation evolution: simple and low cost more complex. for example: (1) the deployment of a radiometer that could provide whole-earth broadband temperature monitoring on the time scale of seconds; (2) the later addition of foreoptics and scanning for progressively better spatial resolution; (3) the final addition of a high resolution spectrometer for multispectral capabilities. Data from such a sensor could be automatically scanned for thermal anomalies and also linked into a sensor network with instruments in GEO or LEO orbits for better feature discriminationon the surface. Dual use: Such a sensor could be ideal of hazard monitoring of fires (location, progression, biomass burning) and volcanoes (new detection, eruption progression, plume tracking).

6 Why the Moon IV

7 Observation from Moon: Pros and Cons PROS CONS Feasibility of synoptic observations (with a single instrument) Global coverage with a single instrument Reduction of the influence of intermittent clouds Reduction of aliasing from daily cycles (i.e. sun periodicity for vegetation, diel winds for coastal waters) Long observation time; feasibility of staring Maintenance, transport and installation Dust Temperature gradients Reduction in signal intensity due to the distance Need for high angular resolution Possibility of increasing integration time Possibility of configuring complex instrumentation at the focal plane Stable temperature environment Stable pointing platform, low seismic activity

8 MAIN OBJECTIVES-scientific studies Earth atmosphere observation Evaluation of observational requirements for weather, clouds, aerosols, gases Ocean observation Study of the evolution of hydrodynamical and thermodinamical parameters Vegetation monitoring Global change and terrestrial carbon cycle Resource management and sustainability Earth radiation budget Earth-Sun interaction, TSI, SSI Georeferencial images Definition of a selenocentric ref. system SECONDARY OBJECTIVES technical requirements study Optical instrumentation Moon based SAR Earth s viewing conditions from the Moon

9 Earth atmosphere observation Evaluation observational requirements (type of sensor, spectral range, resolution) for Climate main aspects relevant to monitoring of tropical cyclones, tornadoes, climate fronts Clouds radiative, chemical, physical properties Aerosols and gases atmospheric chemistry at global and local scale

10 Ocean observation Physical oceanography Mapping of marine currents; ocean circulation; oceanic front identification; Sea Surface Temperature (SST) Mapping Optical Oceanography, water masses characterization Ocean optical properties Ocean color Water quality Sea-ice melting and formation Coverage Temperature of ice sheets and caps Floating oceanic ice Marine ecosystem study Marine biology; fisheries science Phytoplankton, phytobenthos, pollutants, Dissolved Organic Matter (DOM), Harmful Algal Blooming (HAB); primary production by marine phytoplankton Coastal waters and other opticallycomplex waters water quality; suspended matter; DOM; pollutants; eutrophication processes; Pollution monitoring Oil slicks type and thickness; pollutants; waste waters; silt runoff

11 Vegetation monitoring Main scientific themes and subjects Global change and terrestrial carbon cycle, Net Primary Production (NPP) Land cover and use Photosynthesis efficiency Resource management and sustainability, Land use, Classification of natural vegetation / crop inventories Forest management Precision farming Extensive subsistence agriculture Early warning of vegetation/crop stress Disaster management

12 Earth radiation budget Continuously monitoring Sun s variability from Space is mandatory for future reliable Earth climatology: main emphasis is on spectral variations; Continuously monitoring Earth as a whole at shortwaves and longwaves from Space is mandatory as well continuous measurement campaigns over many decades from the Moon bring: advancement of solar physics via the recent solar-dynamo models progressive knowledge of the Earth climatology more sophisticated climatological models.

13 Georeferencing images Definition of a selenocentric ref. System design a needed network of Laser retro-reflector on the moon establishing and maintaining a moon fixed reference system suitable to allow positioning and navigation on a long range scale has to be addressed. Extensive moon exploration, both robotic and human, navigation capability on the Moon To achieve Navigation Capability a Moon centered Reference system is needed LLR not only allows the realization on the moon of a geodetic reference system, but also increase our knowledge of Earth and Moon bridge towards the other scientific studies, in particular that one addressing the study of the moon itself.

14 Optical instrumentation Dimensions of a telescope for Earth observation from the Moon (EPD & FL): 5m EPD 38 m resolution on Resolution vs. wavelength Search for possible configurations: Resolution (m) 1,00E+05 1,00E+04 1,00E+03 1,00E+02 1,00E+01 1,00E+00 0, Wavelength (μm) D=1m D=3m D=5m D=8m D=10m Ritchey-Cretien 3mirror anastigmatic Spectrograph telescope The largest technical constraint to observing the Earth from a lunar base is spatial resolution. At the sub-moon point, the diffraction-limited resolution (R) can be approximated (in km) by R = λ/d λ = wavelength (in microns) D = telescope diameter (in meters). at visible wavelengths a spatial resolution of 1 km or less requires a 1 meter or larger telescope.

15 Two different scenarios: Potentiality of Earth vision from a Moon based SAR 1. SAR system observes the Earth during the transfer from the Earth to the Moon; 2. two or more transmitter-receiver devices are located on the Moon surface and observe the Earth The second scenario appears to be the more promising to stress the potentialities of the system respect to both existing LEO missions and possible future missions on high orbit satellites. Advantageous w.r.t. LEO artificial satellite: On the surface of the Moon some restrictions on the transmitted power, on the antenna dimensions and on the number of antenna and their relative distances are not applicable. A Moon-based SAR can collect data from a very large portion of the surface of the Earth (ex Italy or the Mediterranean basin) Data from a resolution cell with a different angle of incidence can be collected, almost at the same time. The temporal difference between repetition passages is one day for most of the time. Advantageous w.r.t. GEO artificial satellite: A cross-track single pass interferometer with both very long synthetic antennas and baselines of large and very stable dimensions Different views may be acquired simultaneously thus providing a unique configuration for multidimensional (3D and 4D) SAR imaging. The number of antennas and their relative positions can be tailored to the specific applications.

16 Earth s viewing conditions from the Moon 1. Selection of lunar site 2. Observational duty cicle analysis 3. Correlation with other scientific areas of the present study Moon base can provide a global and synoptic view of the Earth's atmosphere, but this capability is strongly affected by Moon phase, astronomical simulations will be set up and carried out in order to determine the Earth's viewing conditions. In particular : Determination of the time-period for which simulations should be carried out, Forecasting of the Moon orbit and estimates of the errors on the forecasting Determination of the geometric parameters relevant to the observation (observation angle, SZA,...)

17 Earth s viewing conditions from the Moon polar areas continuously observed Mid areas observed once/day GOES MeteoSat perspective and

18 Conclusion, remarks, future tasks I main aspects an Earth observatory built on the Moon surface can cover: Continuous full-disk view (sunlit half the time) enables many Earth viewing applications from space with sub-km horizontal resolution: Global mapping of Earth surface and atmosphere Altimetry Coordination of satellite constellations Advantages relative to human-made satellites: Enabling of large telescopes, antennas, power supplies Stability of platform Challenges Terminator crossing complicates radiative transfer Day/night heating differential Dust Moonquakes

19 Conclusion, remarks, future tasks II Simultaneous observation from the Moon and from : geostationary observatories (radiometric crosscalibration between instr) LEO observatories (additional datasets with which to monitor dynamic terrestrial phenomena such as volcanic eruptions, wind storms, and cloud cover) Lagrangian observatories (Sun) lunar Earth observation program could complement Earth-orbiting satellite observation. Synchronized observations of planetary phenomena by multiple sensors and spacecraft have recently demonstrated to be very demanding, but successful,: Jupiter millenium flyby (clues on volcanic eruptions on Io have been explained with instruments onboard Cassini and Ulysses together with ground based observation from the most powerful Earth telescopes of the Keck and Anglo-Australian observatory.) Huygens descent (Cassini+Keck) impact of comet Shoemaker-Levy 9 into Jupiter Final suggestion: a permanent working group on Earth observation from the Moon to draw a roadmap for making the Lunar Earth observatory a reality. A NASA group already exists within NASA Earth Science SUbcommittee