Delta-V Earth-Gravity-Assist Trajectories with Hybrid Solar Electric–Photonic Propulsion

2021 ◽  
pp. 1-9
Author(s):  
Yuki Takao ◽  
Toshihiro Chujo
Keyword(s):  
Gravity Assist ◽  
Earth Gravity

scholarly journals Inter-Calibration of the OSIRIS-REx NavCams with Earth-Viewing Imagers

2019 ◽  
Vol 11 (22) ◽  
pp. 2717 ◽  
Author(s):  
David Doelling ◽  
Konstantin Khlopenkov ◽  
Conor Haney ◽  
Rajendra Bhatt ◽  
Brent Bos ◽  
...  
Keyword(s):  
Spectral Band ◽  
Field Of View ◽  
Space Probe ◽  
Gravity Assist ◽  
Tropical Ocean ◽  
Sensor Performance ◽  
Earth Gravity ◽  
The Earth ◽  
Current Constellation ◽  
Navigation Errors

The Earth-viewed images acquired by the space probe OSIRIS-REx during its Earth gravity assist flyby maneuver on 22 September 2017 provided an opportunity to radiometrically calibrate the onboard NavCam imagers. Spatially-, temporally-, and angularly-matched radiances from the Earth viewing GOES-15 and DSCOVR-EPIC imagers were used as references for deriving the calibration gain of the NavCam sensors. An optimized all-sky tropical ocean ray-matching (ATO-RM) calibration approach that accounts for the spectral band differences, navigation errors, and angular geometry differences between NavCam and the reference imagers is formulated in this paper. Prior to ray-matching, the GOES-15 and EPIC pixel level radiances were mapped into the NavCam field of view. The NavCam 1 ATO-RM gain is found to be 9.874 × 10−2 Wm−2sr−1µm−1DN−1 with an uncertainty of 3.7%. The ATO-RM approach predicted an offset of 164, which is close to the true space DN of 170. The pre-launch NavCam 1 and 2 gains were compared with the ATO-RM gain and were found to be within 2.1% and 2.8%, respectively, suggesting that sensor performance is stable in space. The ATO-RM calibration was found to be consistent within 3.9% over a factor of ±2 NavCam 2 exposure times. This approach can easily be adapted to inter-calibrate other space probe cameras given the current constellation of geostationary imagers.

Absolute Magnetometer Attitude Reconstruction using Magnetospheric Modelling

2020 ◽  
Author(s):  
Johannes Z. D. Mieth ◽  
Daniel Heyner ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Main Magnetic Field ◽  
Main Field ◽  
Gravity Assist ◽  
Earth Gravity ◽  
Simultaneous Measurements ◽  
The Earth ◽  
Sensor Orientation ◽  
The Absolute ◽  
Modelling Approach

<p>One of the main goals of the magnetometer experiment MPO-MAG on board of the Magnetospheric Planetary Orbiter (MPO) during the BepiColombo mission is the determination of the Mercury main magnetic field, epecially in constraining the characteristics of the magnetic dipole offset.<br>In April 2020 BepiColombo had its Earth Gravity Assist manoeuvre on its way to planet Mercury.<br>The topocentric distance was lower than three Earth radii and offered a unique opportunity to compare the magnetometer measurements to a multitude of simultaneous measurements of the magnetospheric environment of the Earth performed by several other spacecraft like THEMIS and MMS.<br>Using a great number of probing points to constrain models of the Earh magnetosphere and compare models to actual measurements of the MPO-MAG sensors enables us to determine the absolute sensor attitude to an accuracy of only a few arc minutes.<br>Knowing the absolute attitude of a magnetometer sensor in planetary orbiter missions is a key component for the magnetic main field determination.<br>We present the modelling approach to compare to measurements from MPO-MAG and a study showing the dependence of a mainfield determination on the accuracy of the sensor orientation.</p>

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