SARA

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SARA (Sub-keV Atom Reflecting Analyzer)

The SARA experiment onboard Chandrayaan-1 was a joint Indo-Swedish collaborative research program between SPL-VSSC and Swedish Institute of Space Physics (IRF), Kiruna, Sweden with participation from Japan (JAXA), and Switzerland (University of Bern). The main objective of the SARA experiment was to study lunar-solar wind interaction by means of the Energetic Neutral Atoms (ENAs) and the charged particles produced as a result of solar wind interaction with the lunar surface. The three components of the SARA experiment were: two sensors - CENA (Chandrayaan-1 Energetic Neutral Analyzer), which detected low energy neutral atoms in the 10-3300 keV energy range, and SWIM (Solar WInd Monitor), which measured the plasma flux in the near-lunar environment in the 10-3000 eV energy range, and the DPU (Digital Processing Unit) which commanded and controlled the operations on both the sensors. Both sensors had a fan shaped Field of View (FoV). Onboard commissioning of SARA was successfully completed in January 2009, and the planned normal operations began in February 2009. SARA performed well till the end of the mission. The measurements made by SARA have yielded many novel and path breaking scientific results - some of which are listed below


  • Observation of large (up to 20%) and sustained backscattering of solar wind protons as ENAs due to the interaction of solar wind with lunar surface.
  • The scattering function for the backscattered ENAs derived from the observations found to be different from the conventional expectations.
  • Discovery of Mini-magnetosphere on Moon.
  • Observation of reflected solar wind protons from dayside lunar surface and their dependence on the solar wind velocity.
  • Higher deflection of solar wind protons from magnetic anomalies (up to 50%).
  • Entry of solar wind protons to deeper lunar wake by diffusion along Interplanetary Magnetic Field.
  • First observation of solar wind protons in the lunar wake during condition of magnetic aligned flow.
  • Large positive surface potential at magnetic anomaly region derived from the observed ENA backscattering. Surface potential <+135 V is found inside the Gerasimovich magnetic anomaly region.
  • Observation of pick-up ions in lunar vicinity.
  • Global map of ENAs from Moon.
  • First observation of solar wind sputtering of the lunar surface. Neutral oxygen atoms were observed whose source process was identified as the sputtering of the lunar surface by the solar wind.
  • Estimation of shielding strength of several magnetic anomalies as a function of solar wind dynamic pressure and the filed strength of the anomaly.
  • Observation of backscattered hydrogen ENAs in the Earth's magnetotail and their characteristics.
  • Almost no dependance of ENA backscattering on surface properties using South Polen Aitken Terrain as a sample region.
  • Characteristics of proton velocity distributions in lunar wake and their source processes.

 

Publications from SARA experiment

  1. Bhardwaj, A., S. Barabash, Y. Futaana, Y. Kazama, K. Asamura, R. Sridharan, M. Holmström, P. Wurz, and R. Lundin, "Low Energy Neutral Atom Imaging on the Moon with the SARA Instrument aboard Chandrayaan-1 Mission", Journal of Earth System Sciences, 114 (6), 749-760, 2005.
  2. Barabash, S., A. Bhardwaj, M. Wieser, R. Sridharan, T. Kurian, S. Varier, E. Vijayakumar, V. Abhirami, K. V. Raghavendra, S. V. Mohankumar, M. B. Dhanya, R. S. Thampi, K. Asamura, H. Andersson, Y. Futaana, M. Holmström, R. Lundin, J. Svensson, S. Karlsson, R. D. Piazza, and P. Wurz, "Investigation of the solar wind-Moon interaction onboard Chandrayaan-1 mission with the SARA Experiment", Current Science, 96, 526-532, 2009.
  3. Wieser, M., S. Barabash, Y. Futaana, M. Holmström, A. Bhardwaj, R. Sridharan, M. B. Dhanya, P. Wurz, A. Schaufelberger, and K. Asamura, "Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space", Planetary and Space Science, 57, 2131-2134, 2009. (http://dx.doi.org/10.1016/j.pss.2009.09.012)
  4. Wieser, M., S. Barabash, Y. Futaana, M. Holmström, A. Bhardwaj, R. Sridharan, M. B. Dhanya, P. Wurz, A. Schaufelberger, and K. Asamura, "First Observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms", Geophysical Research Letters, 37, L05103, 2010. (http://dx.doi.org/10.1029/2009GL041721)
  5. Holmström, M., M. Wieser, S. Barabash, Y. Futaana, and A. Bhardwaj, "Dynamics of solar wind protons reflected by the Moon", Journal of Geophysical Research, 115, A06206, 2010. (http://dx.doi.org/10.1029/2009JA014843)
  6. Futaana, Y., S. Barabash, M. Wieser, M. Holmström, A. Bhardwaj, M. B. Dhanya, R. Sridharan, P. Wurz, A. Schaufelberger, and K. Asamura, "Protons in the lunar wake observed by the SARA instrument on board Chandrayaan-1", Journal of Geophysical Research, 115, A10248, 2010. (http://dx.doi.org/10.1029/2010JA015264)
  7. Bhardwaj, A., S. Barabash, M. B. Dhanya, M. Wieser, Y. Futaana, M. Holmström, R. Sridharan, P. Wurz, A. Schaufelberger, and K. Asamura, "Studying the lunar-solar wind interaction with the SARA experiment aboard the Indian Lunar Mission Chandrayaan-1", in SOLAR WIND TWELVE: Proceedings of the Twelfth International Solar Wind Conference, AIP Conference Proceedings, 1216, 518-521, 2010.
  8. Bhardwaj, A., M. Wieser, M. B. Dhanya, S. Barabash, Y. Futaana, M. Holmström, R. Sridharan, P. Wurz, A. Schaufelberger, and K. Asamura, "The Sub-keV Atom Reflecting Analyzer (SARA) Experiment aboard Chandrayaan-1 mission: Instrument and Observations", Advances in Geosciences, 19, 151-162, 2010.
  9. Lue, C., Y. Futaana, S. Barabash, M. Wieser, M. Holmström, A. Bhardwaj, M. B. Dhanya, and P. Wurz, "Strong influence of lunar crustal fields on the solar wind flow", Geophysical Research Letters, 38, L03202, 2011. (http://dx.doi.org/10.1029/2010GL046215)
  10. Schaufelberger, A., P. Wurz, S. Barabash, M. Wieser, Y. Futaana, M. Holmström, A. Bhardwaj, M. B. Dhanya, R. Sridharan, and K. Asamura, "Scattering function for energetic neutral hydrogen atoms off the lunar surface", Geophysical Research Letters, 38, L22202, 2011. (http://dx.doi.org/10.1029/2011GL049362)
  11. Vorburger, A., P. Wurz, S. Barabash, M. Wieser, Y. Futaana, M. Holmström, A. Bhardwaj, and K. Asamura, "Energetic neutral atom observations of magnetic anomalies on the lunar surface", Journal of Geophysical Research, 117, A07208, 2012. (http://dx.doi.org/10.1029/2012JA017553)
  12. Futaana, Y., S. Barabash, M. Wieser, M. Holmström, C. Lue, P. Wurz, A. Shaufelberger, A. Bhardwaj, M. B. Dhanya, and K. Asamura, "Empirical energy spectra of neutralized solar wind protons from the lunar regolith", Journal of Geophysical Research, 117, E05005, 2012. (http://dx.doi.org/10.1029/2011JE004019)
  13. Bhardwaj, A., M. B. Dhanya, R. Sridharan, S. Barabash, Y. Futaana , M. Wieser, M. Holmström, C. Lue, P. Wurz, A. Schaufelberger, and K. Asamura, "Interaction of solar wind with Moon: An Overview on the results from the SARA experiment aboard Chandrayaan-1", Advances in Geosciences, 25, 35-56, 2012.
  14. Vorburger, A., P. Wurz, S. Barabash, M. Wieser, Y. Futaana, C. Lue, M. Holmström, A. Bhardwaj, M. B. Dhanya, and K. Asamura, "Energetic neutral atom imaging of the lunar surface", Journal of Geophysical Research, 118 (7), 3937-3945, 2013. (http://dx.doi.org/10.1002/jgra.50337)
  15. Futaana, Y., S. Barabash, M. Wieser, C. Lue, P. Wurz, A. Vorburger, A. Bhardwaj, and K. Asamura, "Remote nergetic neutral atom imaging of electric potential over a lunar magnetic anomaly", Geophysical Research Letters, 40 (2), 262-266, 2013. (http://dx.doi.org/10.1002/grl.50135)
  16. Dhanya, M. B., A. Bhardwaj, Y. Futaana, M. Holmström, S. Barabash, M. Wieser, S. Fatemi, P. Wurz, A. Alok, and R. S. Thampi, "Proton entry into the near-lunar plasma wake for magnetic field aligned flow", Geophysical Research Letters, 40 (12), 2913-2917, 2013. (http://dx.doi.org/10.1002/grl.50617)
  17. Vorburger, A., P. Wurz, S. Barabash, M. Wieser, Y. Futaana, M. Holmström, A. Bhardwaj, and K. Asamura, "First direct observation of sputtered lunar oxygen", Journal of Geophysical Research, 119, 1-14, 2014. (http://dx.doi.org/10.1002/2013JA019207)
  18. Lue, C., Y. Futaana, M. Wieser, S. Barabash, A. Bhardwaj, and P. Wurz, "Chandrayaan-1 observations of backscattered solar wind protons from the lunar regolith: Dependence on solar wind velocity", Journal of Geophysical Research, 119, 968-975, 2014. (http://dx.doi.org/10.1002/2013JE004582)
  19. Harada, Y., Y. Futaana, S. Barabash, M. Wieser, P. Wurz, A. Bhardwaj, K. Asamura, Y. Saito, S. Yokota, H. Tsunakawa, and S. Machida, "Backscattered Energetic Neutral Atoms from the Moon in the Earth's plasma sheet observed by Chandarayaan-1/SARA instrument", Journal of Geophysical Research, 1-12, 2014. (http://dx.doi.org/10.1002/2013JA019682)
  20. Bhardwaj, A., M. B. Dhanya, A. Alok, S. Barabash, M. Wieser, Y. Futaana, P. Wurz, A. Vorburger, M. Holmstrom, C. Lue, Y. Harada, and K. Asamura (2015), "A New View on Solar wind interaction with Moon", Geosciences Letters (http://dx.doi.org/10.1186/s40562-015-0027-y).
  21. Vorburger, A., P. Wurz, S. Barabash, M. Wieser, Y. Futaana, A. Bhardwaj, and K. Asamura (2015), "Imaging the South Pole - Aitken Basin in Backscattered Neutral Hydrogen Atoms", Planetary and Space Science, in press (http://dx.doi.org/10.1016/j.pss.2015.02.007).
  22. Dhanya, M. B., A. Bhardwaj, Y. Futaana, S. Barabash, A. Alok, M. Wieser, Mats Holmström, and P. Wurz (2016), "Characteristics of proton velocity distribution functions in the near-lunar wake from Chandrayaan-1/SWIM observations", Icarus, 271, 120-130, doi: 10.1016/j.icarus.2016.01.032.
  23. Lue, C., Y. Futaana, S. Barabash, Y. Saito, M. Nishino, M. Wieser, K. Asamura, A. Bhardwaj, and P. Wurz (2016), "Scattering characteristics and imaging of energetic neutral atoms from the Moon in the terrestrial magnetosheath", Journal of Geophysical Research, in press, doi:10.1002/2015JA021826.

 

psb/sara.jpg

 

Press Release on SARA by European Space Agency

Geophysical Research Letters Highlights on SARA

Cover Page of GRL Highlighting SARA Results

Poster on SARA

 

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