Science Systems and Applications, Inc. - Science and Technology with Passion


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Intern - Global Ecosystem Dynamics Investigation (GEDI)
Reference #:21-3075
Open Date:4/6/2021
US Citizenship Required:No
Job Description:

Science Systems and Applications, Inc (SSAI) is seeking a 2021 Summer Intern to help support the Global Ecosystems Dynamics Investigation (GEDI) instrument. Launched to International Space Station (ISS) in December of 2018, the Global Ecosystem Dynamics Investigation (GEDI) instrument began collecting scientific data in operational mode on April 17th, 2019.  GEDI is currently scheduled as a two-year mission and is producing high resolution laser ranging observations of the 3D structure of the Earth.  The fundamental geodetic measurement used to achieve these mission science objectives is the geolocation of individual laser waveform returns. Geolocation is computed as a function of three complex measurements: (1) the position of the instrument in inertial space, (2) the pointing of each individual laser beam in inertial space, and (3) the laser waveform round trip travel time observation. GEDI Precision Pointing Determination (PPD) is responsible for computing the second of these; the precise pointing of each laser. PPD is comprised of the Precision Attitude Determination (PAD) of the GEDI Optical Bench Frame (OBF) with respect to inertial space, and the calibration of the laser pointing with respect to the OBF. 

Improvements in the GEDI mission PAD solution are key to improving the GEDI mission geolocation.  Improved geolocation significantly reduces the GEDI science data product errors and advances GEDI data applications to ecosystem science, as well as solid earth, hydrology, and cryosphere sciences.

GEDI PAD is accomplished with 3 DTU Star Tracker heads. Each head comes with an integrated MEMS micro inertial reference unit (MIRU). Due to a restricted field of view, as well as the harsh glinting and blockage environment on the ISS, all trackers are often blinded and present challenges to achieving an optimal PAD solution. The ground post-processed PAD implements a Multiplicative Extended Kalman Filter (MEKF) and Rauch-Tung-Striebel (RTS) filter. The filter states include attitude corrections to the attitude reference frame, angular rate bias estimates which are removed from the angular rate data, and relative alignment states to each tracker. The GEDI mission’s challenging geolocation budget requires attitude solutions to be better than 4.5 arcseconds 1s (9 m horizontal geolocation error), with an overall geolocation knowledge budget of 10 m.  This internship focuses on improving the GEDI PAD solutions through the correlation of Star Tracker head temperature telemetry to develop an empirically derived temperature correction model.  The internship includes the identification of optimal test time periods, the collection and parsing of the test data, support the development of the correction model, and perform evaluation tests.

This is a 100% virtual internship. Computer resources and all required software will be provided.

Required Qualifications:
  • Engineering, Physics, or Math, STEM discipline focused education.
  • Experience in MATLAB or another programming/analysis language, or willingness to learn a new programming language.
  • Excellent communication skills, with experience in MS Word and Powerpoint
Desired Qualifications:
  • Knowledge and or experience with spacecraft attitude determination and attitude dynamics.
  • Knowledge and or experience in spacecraft orbit mechanics.