Jettison Engineering Trajectory Tool Lyndon B. Johnson Space Center, Houston, Texas The Jettison Engineering Trajectory days to complete to one that can be com - for maintaining data entered by the user Tool (JETT) performs the jettison analy - pleted in hours, with an analysis that is and generated by the analysis. The view sis function for any orbiting asset. It pro - more comprehensive than the previous category provides capabilities for data vides a method to compute the relative method. It provides the ability to define entry and displaying all or a portion of trajectories between an orbiting asset the jettison operation relative to Interna - the analysis data in tabular, 2D, and 3D and any jettisoned item (intentional or tional Space Station (ISS) structure, and representation. The controller category unintentional) or sublimating particles provides 2D and 3D plotting capability to allows for handling events that affect the generated by fluid dumps to assess allow an analyst to perform a subjective model or view(s). The JETT utilizes or - whether an object is safe to jettison, or if clearance assessment with ISS structures. bital mechanics with complex algo - there is a risk with an item that was inad - The developers followed the SMP to rithms. Since JETT is written in JAVA, it vertently lost overboard. The main con - create the code and all supporting docu - is essentially platform-independent. cern is the interaction and possible re- mentation. The code makes extensive This work was done by Mariusz Zaczek of contact of the jettisoned object with an use of the object-oriented format of Java Johnson Space Center; and Patrick Walter, asset. This supports the analysis that jet - and, in addition, the Model-View-Con - Joseph Pascucci, Phyllis Armstrong, Patricia tisoned items will safely clear the vehicle, troller architecture was used in the or - Hallbick, Randal Morgan, and James ensuring no collisions. ganization of the code, allowing each Cooney of the United Space Alliance. Further The software will reduce the jettison piece to be independent of updates to information is contained in a TSP (see page analysis task from one that could take the other pieces. The model category is 1) . MSC-25271-1

MPST Software: grl_suppdoc NASA’s Jet Propulsion Laboratory, Pasadena, California

Due to the nature of the GRAIL mis - The grl_suppdoc tool enables the GRAIL quired for GRAIL sequence team opera - sion, the GRAIL Mission Planning and MPST to generate automatically Deep tions. Compared to a manual process, Sequence Team (MPST) is required to Space Network (DSN) transmitter sup - this script reduces human error and generate ground and uplink products pressions based on short uplinks that are saves considerable man-hours by au - faster than ever done before. The exist - found in the ground/modeled Predicted tomating and streamlining the mission ing correct_transmitter_min_dur tool Events File (PEF). planning and sequencing task for the that provides a similar function to The grl_suppdoc script automatically GRAIL mission. grl_suppdoc lacks the ability to operate generates applicable DSN uplink sup - This work was done by Jared A. Call and accurately or quickly enough to support pressions in the form of a Spacecraft Ac - John H. Kwok of Caltech for NASA’s Jet the rapid turnaround required of the tivity Sequence File (SASF) to protect Propulsion Laboratory. For more information, GRAIL MPST. the GRAIL project from short DSN up - contact iaoffice@jpl.nasa.gov. The GRAIL MPST was required to link windows, which can be cause for op - This software is available for commercial li - build this new tool to facilitate the ground erator error at the DSN antennas. Cur - censing. Please contact Dan Broderick at and uplink generation processes to meet rently, no software exists that provides [email protected]. Refer to a tight sequence development timeline. this functionality at the efficiency re - NPO-48659.

PredGuid+A: Orion Entry Guidance Modified for Aerocapture Lyndon B. Johnson Space Center, Houston, Texas

PredGuid+A software was developed to PredGuid+A allows the user to set a scenarios for NASA’s Orion multi-pur - enable a unique numerical predictor-cor - mode flag and input a target orbit’s pose crew vehicle (MPCV). To leverage rector aerocapture guidance capability apoapsis and periapsis. Using bank flight heritage, most of Orion’s entry that builds on heritage Orion entry guid - angle control, the guidance will then guidance routines are adapted from the ance algorithms. The software can be used guide the vehicle to the appropriate Apollo program. for both planetary entry and aerocapture post-aerocapture orbit using one of This work was done by Jarret Lafleur of applications. Furthermore, PredGuid+A two algorithms: Apoapsis Targeting or Johnson Space Center. Further information is implements a new Delta-V minimization Delta-V Minimization (as chosen by contained in a TSP (see page 1) . MSC- guidance option that can take the place of the user). 25199-1 traditional targeting guidance and can re - Recently, the PredGuid guidance algo - sult in substantial propellant savings. rithm was adapted for use in skip-entry

44 NASA Tech Briefs, September 2013