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Lee, Julim

Publications and source records attributed to Lee, Julim.

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Navigation Design and Operations of Maven Aerobraking

This paper describes the operational design and execution of the MAVEN aerobraking phase at Mars from a Navigation Team perspective. MAVEN was designed to perform atmospheric science in a ~150x6200 km altitude elliptical orbit. After the primary science mission, it was decided that MAVEN should circularize its orbit, as much as feasible from a spacecraft and mission standpoint, to better support relay operations with the landers. As a result, MAVEN performed aerobraking in the first half of 2019 to reduce its orbit to ~150x4500 km altitude. Although MAVEN did not decrease its altitude as low as previous aerobraking missions, it had several unique challenges. Science observations continued to be taken during aerobraking, requiring dramatically better Navigation accuracies than typical for such phases. Furthermore, continuous DSN coverage with 2-way Doppler data was not available. So, with 40% less Doppler data, Navigation had to meet prediction accuracies which were an order of magnitude smaller than in previous aerobraking operations. Spacecraft accelerometer data was included in Navigation analyses in order to meet these requirements.

Jakosky, Bruce↗
NASA NTRS2019

2018 Mars Insight Trajectory Reconstruction and Performance from Launch Through Landing

The InSight mission successfully launched to Mars on an Atlas V 401 launch vehicle from the Western Test Range (WTR) at Vandenberg Air Force Base (VAFB) at 04:05:00 PDT on May 5th, 2018 and landed in the Elysium Planitia Region on November 26th, 2018. Data confirming nominal touchdown was received at 11:52:59 AM PST. This paper summarizes in detail the actual vs. predicted performance of the InSight spacecraft and all associated assets in terms of launch vehicle events, injection performance, DSN performance, cruise performance, and Entry, Descent, and Landing events.

Abilleira, Fernando↗
NASA NTRS2019

InSight attitude control system thruster characterization and calibration for successful navigation to Mars

In order for the InSight spacecraft to execute a safe Mars landing, it was crucial that the navigation team accurately predict the trajectory and deliver the spacecraft to the targeted atmospheric entry point. One of the primary challenges faced by the Navigation Team was the accurate reconstruction and prediction of small but frequent velocity changes imparted by the spacecraft’s Attitude Control System thrusters. This paper discusses the in-flight thruster calibration campaign, the reconstruction and prediction of accelerations throughout various phases of cruise (including compensating for significant outgassing after launch and attitude transition), and the subsequent impact on atmospheric entry point delivery

McCandless, Sarah Elizabeth↗
NASA NTRS2019

InSight orbit determination

The InSight mission relied on accurate deep-space navigation for a successful Mars landing on November 26, 2018. In this paper, we discuss the role of the cruise Orbit Determination team, whose responsibilities included determining the spacecraft state, predicting the future trajectory, and quantifying the uncertainty associated with those estimates. In particular, we will focus on spacecraft dynamic modeling, small forces due to attitude control, radiometric tracking data, filter strategies, uncertainty quantification, and responses to unexpected flight situations. We will also provide analysis of reconstructed maneuvers, small forces, and delivery accuracy at Mars arrival.

Seubert, Jill↗
NASA NTRS2019

Navigation performance of the 2018 InSight Mars Lander mission

The NASA InSight spacecraft was launched successfully from Vandenberg Air Force Base on an Atlas V 401 launch vehicle on May 5, 2018 and landed on November 26, 2018. Accurate targeting to the atmospheric entry point by the Navigation team achieved by carefully controlling the final entry flight path angle to -12.0 degrees with a tolerance of +/- 0.21 degrees. This paper will describe how the InSight Navigation team met this difficult task in the presence of frequent unbalanced thrusting for attitude control. The continuous correction for this unplanned ∆V far exceeded pre-launch expectations and proved a challenge to predict accurately.

Wallace, Mark↗
NASA NTRS2018

2018 Mars Insight Mission Design and Navigation Overview

Originally scheduled for a launch in the 2016 Earth to Mars opportunity, NASA’s Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission will launch the next lander to Mars in May-June 2018 arriving to the Red Planet in November 2018. Derived from the Phoenix mission which successfully landed on Mars in May 2008, the InSight Entry, Descent, and Landing system will place a lander in the Elysium Planitia region. This paper specifies the mission and navigation requirements set by the Project and how the final mission and navigation design satisfies those requirements.

Abilleira, Fernando↗
NASA NTRS2017

Navigation automation for the Soil Moisture Active Passive observatory

Soil Moisture Active Passive (SMAP) is a NASA Earth science mission designed to measure soil moisture content and freeze/thaw cycles over a three-year period. This paper presents a 2-year summary of navigation performance, shows navigation compliance (and non-compliance) with Science Orbit Requirements, and describes how automated processes appreciably reduced the size of the navigation team.

Lee, Julim↗
NASA NTRS2016

MAVEN Navigation During the First Mars Year of the Science Mission

The Mars Atmosphere and Volatile Evolution mission (MAVEN) is the first mission devoted to studying the Martian atmosphere. From a Navigation perspective it is unique in that science is performed at near aerobraking altitudes. This results in the requirements on Navigation trajectory accuracy requirements which are an order of magnitude tighter than those of aerobraking phases on previous missions. Navigation experiences with the Mars atmosphere are described as they pertain to Navigation models, trajectory reconstructions, trajectory predictions, density corridor control, and collision avoidance of other bodies around Mars.

Demcak, Stuart↗
NASA NTRS2016

Final Mission and Navigation Design for the 2016 Mars InSight Mission

NASA’s Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission was scheduled to launch the next lander to Mars in March 2016 arriving to the Red Planet in the fall. Derived from the Phoenix mission which successfully landed on Mars in May 2008, the InSight Entry, Descent, and Landing system will place a lander in the Elysium Planitia region. This paper specifies the mission and navigation requirements set by the Project and how the final mission and navigation design satisfies those requirements. Background information affecting navigation including spacecraft modeling and the physical environment which influences the spacecraft motion are included. (Note from the author: The InSight launch in 2016 was suspended due to critical issues with the Seismic Experiment for Interior Structure (SEIS) instrument that could not be fixed prior to the planned launch period. This paper represents the state of the design for the 2016 mission. No attempt has been made to reflect the latest developments).

Abilleira, Fernando↗
NASA NTRS2015

Odyssey Mars Orbiter - Thirteen Years of On-Orbit Navigation

The Odyssey spacecraft has been in Mars orbit since October 24, 2001 and has nearly completed 61,490 orbits. Navigation operational objectives include the following: Control the local mean solar time for science observations; for most of the mission, this varied from 3:45 pm to 5:20 pm. Currently, an orbit trim maneuver planned for November 10, 2015 will place Odyssey at 6:45 pm/6:45 am at equator crossings in order to observe early morning ground frost, fog and clouds. Initially, Odyssey was late by 42 minutes for an over-flight of the critical seven minutes of Phoenix's entry, descent and landing (EDL). Odyssey was successfully positioned for this over-flight using the Delta V from angular momentum desaturations (AMD). Similar results for the Mars Science Laboratory's EDL and Comet Siding Spring's minimum risk location will be presented. Odyssey has and continues to relay significant quantities of rover data. Navigation successfully models frequent AMD Delta Vs in order to generate accurate sixty-day trajectory predictions; a typical timing error is 25 seconds after 60 days. However, unexpected events, such as safe-mode entries with their larger and more frequent thrusting, severely impact that trajectory accuracy. Impacted trajectories can have timing errors ranging from a few minutes to ten-to-fifteen minutes after sixty-days. Other analyses (briefly stated) include: a) the offset of the orbital ground track pattern after an initial cycle of 30 days or 362 orbits and b) an operations environment of continuous thrusting if/when one of the three remaining reaction wheels fails.

trajectory accuracy↗