Search NASA⌕ Search

SEARCH · Search NASA

Results for “orbit trim maneuver”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Reducing Pointing Errors During Cassini Reaction Control System Orbit Trim Maneuvers

The effect of altering a gain parameter in the Cassini reaction control system (RCS) delta-V controller on the maneuver execution errors during orbit trim maneuvers (OTMs) is explored. Cassini consists of two reaction control thruster branches (A & B) each with eight thrusters. Currently, the B-branch is operational while the A-branch serves as a back-up. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. During an OTM, the Z-thrusters fire to maintain the X and Y-axes pointing within an attitude control dead-zone (-10 to 10 milliradians). The errors do not remain at zero due to pointing error sources such as spacecraft center of mass offset from the geometric center of the Z-facing thrusters, and variability in the thruster forces due to the thruster hardware differences. The delta-V reaction control system (RCS) controller ensures that the attitude error remains within this dead-zone. Gain parameters within the RCS delta-V controller affect the maneuver execution errors. Different parameter values are used to explore effect on these errors. It is found that pointing error decreases and magnitude error increases rapidly for gain parameters 10 times greater than the current parameter values used in the flight software.

European Space Agency (ESA)↗
NASA NTRS2011

Cassini Orbit Trim Maneuvers at Saturn - Overview of Attitude Control Flight Operations

The Cassini spacecraft has been in orbit around Saturn since July 1, 2004. To remain on the planned trajectory which maximizes science data return, Cassini must perform orbit trim maneuvers using either its main engine or its reaction control system thrusters. Over 200 maneuvers have been executed on the spacecraft since arrival at Saturn. To improve performance and maintain spacecraft health, changes have been made in maneuver design command placement, in accelerometer scale factor, and in the pre-aim vector used to align the engine gimbal actuator prior to main engine burn ignition. These and other changes have improved maneuver performance execution errors significantly since 2004. A strategy has been developed to decide whether a main engine maneuver should be performed, or whether the maneuver can be executed using the reaction control system.

spacecraft configuration↗
NASA NTRS1978

Orbit trim maneuver design and implementation for the 1975 Mars Viking Mission

The Viking Mission included the insertion of two unmanned spacecraft into orbit about Mars and the deployment of a soft-lander from each. A description is presented of the adaptive design and implementation of the spacecraft propulsive maneuvers as these flights progressed, taking into account also the inflight results for the orbital phase of the primary Viking mission. The design process included the selection of target parameters and the minimization of both propellant usage and the effects of execution errors, while complying with mission and operational constraints. All maneuvers performed to trim the spacecraft orbits are considered. Attention is given to navigation requirements, geometry definitions and terminology, maneuver mechanization and constraints, and maneuver capability.

Hintz, G. R.↗
NASA NTRS2008

Three year orbital trim maneuver performance of the Cassini spacecraft attitude control subsystem.

Cassini is a sophisticated interplanetary spacecraft providing scientific findings that continue to offer insight into our solar system. After arriving at Saturn on June 30, 2004 it has completed three years of a four year prime mission. To date, Cassini has completed 49 orbits about Saturn and over 40 targeted flybys of Saturn’s moons. This has been achieved with a nominal design using three delta-V maneuvers per targeted encounter.

Smith, Brett A.↗
NASA NTRS2018

A Full Mission Summary (1997-2017) of the Attitude Control Performance during Orbit Trim Maneuvers Performed by the Cassini-Huygens Spacecraft

The Cassini mission was a highly successful 20-year mission to the planet Saturn that launched in 1997 and concluded its mission in September 2017. Over the course of its mission, Cassini executed hundreds of main engine and thruster-controlled ΔV maneuvers. This paper provides an overview of the Cassini maneuvers and provides data on the performance of the attitude controller and maneuver execution errors during these maneuvers. The paper concludes with an appendix documenting the vital statistics for all maneuvers that Cassini performed.

Brown, Todd S.↗
NASA NTRS1986

Maneuver strategies for the Magellan (Venus radar mapper) mission

The paper describes the maneuver strategies for the Venus Orbit Insertion and the Orbit Trim Maneuvers for the Magellan mission. An optimum three impulse strategy has been developed for the Venus Orbit insertion maneuver that minimizes the fuel consumed during the trim maneuvers. In addition an optimum two impulse strategy has been designed specifically for the two trim maneuvers that minimizes the fuel consumed while correcting for period, periapsis altitude, argument of periapsis, and inclination.

Dsouza, C. N.↗
NASA NTRS1972

A Monte Carlo error analysis program for near-Mars, finite-burn, orbital transfer maneuvers

A computer program was developed which performs an error analysis of a minimum-fuel, finite-thrust, transfer maneuver between two Keplerian orbits in the vicinity of Mars. The method of analysis is the Monte Carlo approach where each off-nominal initial orbit is targeted to the desired final orbit. The errors in the initial orbit are described by two covariance matrices of state deviations and tracking errors. The function of the program is to relate these errors to the resulting errors in the final orbit. The equations of motion for the transfer trajectory are those of a spacecraft maneuvering with constant thrust and mass-flow rate in the neighborhood of a single body. The thrust vector is allowed to rotate in a plane with a constant pitch rate. The transfer trajectory is characterized by six control parameters and the final orbit is defined, or partially defined, by the desired target parameters. The program is applicable to the deboost maneuver (hyperbola to ellipse), orbital trim maneuver (ellipse to ellipse), fly-by maneuver (hyperbola to hyperbola), escape maneuvers (ellipse to hyperbola), and deorbit maneuver.

Green, R. N.↗
NASA NTRS2018

Flying Cassini Through the Grand Finale Orbits: Prediction vs. Reality

After twenty years of successful mission operations and invaluable scientific discoveries, the Cassini orbiter completed its tour around the Saturnian system on the most complex gravity-assist trajectory ever flown. The end-of-mission target of September 15, 2017 was achieved by preserving propellant at the expense of minimizing maneuver cycles. A navigation a strategy that incorporated orbit trim maneuvers was developed years in advance to maintain position dispersions below 250 km (1σ) at three specific periapses. This paper reports on the actual maneuver performance and overall trajectory control to maintain the Grand Finale orbits, highlighting the differences between predicted and implemented values.

Roth, Duane↗
NASA NTRS2011

Characterizing Observed Limit Cycles in the Cassini Main Engine Guidance Control System

The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur due to the interaction between the unmodeled nonlinear elements and linear ME guidance controller.

stable limit cycle↗
NASA NTRS2008

Cassini's Maneuver Automation Software (MAS) Process: How to Successfully Command 200 Navigation Maneuvers

To keep Cassini on its complex trajectory, more than 200 orbit trim maneuvers (OTMs) have been planned from July 2004 to July 2010. With only a few days between many of these OTMs, the operations process of planning and executing the necessary commands had to be automated. The resulting Maneuver Automation Software (MAS) process minimizes the workforce required for, and maximizes the efficiency of, the maneuver design and uplink activities. The MAS process is a well-organized and logically constructed interface between Cassini's Navigation (NAV), Spacecraft Operations (SCO), and Ground Software teams. Upon delivery of an orbit determination (OD) from NAV, the MAS process can generate a maneuver design and all related uplink and verification products within 30 minutes. To date, all 112 OTMs executed by the Cassini spacecraft have been successful. MAS was even used to successfully design and execute a maneuver while the spacecraft was in safe mode.

Yang, Genevie Velarde↗
NASA NTRS1972

Maneuver design and implementation for the Mariner 9 mission.

The maneuver strategy and operational techniques employed in controlling the Mariner 9 flight path from earth launch, through interplanetary space, Mars orbit insertion, and the subsequent orbital trim maneuvers are presented. It is shown how the maneuver strategy was tailored to meet the mission requirements with maximum reliability in the presence of launch vehicle injection, orbit determination, and spacecraft maneuver execution errors as great as 3 sigma. The major error sources and constraints are discussed. The in-flight results are summarized and are compared with the preflight predictions.

Mitchell, R. T.↗
NASA NTRS1973

Satellite orbit determination

A historic account of the activities of the Satellite OD Group during the MM'71 mission is given along with an assessment of the accuracy of the determined orbit of the Mariner 9 spacecraft. Preflight study results are reviewed, and the major error sources described. Tracking and data fitting strategy actually used in the real time operations is itemized, and Deep Space Network data available for orbit fitting during the mission and the auxiliary information used by the navigation team are described. A detailed orbit fitting history of the first four revolutions of the satellite orbit of Mariner 9 is presented, with emphasis on the convergence problems and the delivered solution for the first orbit trim maneuver. Also included are a solution accuracy summary, the history of the spacecraft orbit osculating elements, the results of verifying the radio solutions with TV imaging data, and a summary of the normal points generated for the relativity experiment.

Jordan, J. F.↗
NASA NTRS2012

Cassini Solstice Mission Maneuver Experience: Year Two

The Cassini Spacecraft was launched in October 1997 on a mission to observe Saturn and its moons; it entered orbit around Saturn in July 2004 for a nominal four-year Prime Mission, later augmented by two extensions: the Equinox Mission, from July 2008 through September 2010, and the Solstice Mission, from October 2010 through September 2017. This paper provides an overview of the maneuver activities from August 2011 through June 2012 which include the design of 38 Orbit Trim Maneuvers--OTM-288 through OTM-326-- for attaining 14 natural satellite encounters: seven with Titan, six with Enceladus, and one with Dione.

navigation↗
NASA NTRS2015

Trajectory Dispersion Control for the Cassini Grand Finale Mission

The Cassini Grand Finale Mission, which consists of 22 ballistic orbits, will begin on April 22, 2017 after the last targeted Titan flyby. It will end on September 15, 2017 when the spacecraft dives into Saturn's atmosphere and be permanently captured. High volumes of unique science data from various onboard instruments are expected from the mission. To ensure its success and facilitate science planning, the trajectory dispersion needs to be controlled below 250 km (root-mean-square spatial deviation at the 68th percentile level) for a few segments of trajectory in the mission. This paper reports the formulation and solution of this dispersion control problem. We consider various sources of uncertainties including flyby error, orbit determination error, maneuver execution error, thruster firing control error, and uncertainty in Saturn's atmospheric model. A non-linear Monte Carlo Trajectory Dispersion tool is developed and employed for the analysis. It is found that a total of three Orbit Trim Maneuvers with a 99% (Delta)V usage of less than 2 m/s will adequately control the trajectory.

orbit determination↗
NASA NTRS2008

Orbit Control Operations for the Cassini-Huygens Mission

The Cassini-Huygens spacecraft was launched in 1997 as an international and collaborative mission to study Saturn and its many moons. After a seven-year cruise, Cassini began orbiting Saturn for a four- year tour. This tour consists of 157 planned maneuvers, and their back-up locations, designed to target 52 encounters, mostly of Saturn's largest moon Titan. One of the mission's first activities was to release the Huygens probe to Titan in December 2004. Currently in its last year of the prime mission, Cassini-Huygens continues to obtain valuable data on Saturn, Titan, and Saturn's other satellites. Return of this information is in large part due to a healthy spacecraft and successful navigation. A two-year extended mission, beginning July 2008, will offer the opportunity to continue science activities. With a demanding navigation schedule that compares with the prime tour, the Cassini Navigation team relies on operations procedures developed during the prime mission to carry-out the extended mission objectives. Current processes for orbit control operations evolved from the primary navigational requirement of staying close to predetermined targeting conditions according to Cassini science sequence planning. The reference trajectory is comprised of flyby conditions to be accomplished at minimal propellant cost. Control of the planned reference trajectory orbit, and any trajectory updates, is achieved with the execution of Orbit Trim Maneuvers (OTMs). The procedures for designing, processing, and analyzing OTMs during Cassini operations is presented. First, a brief overview of the Cassini-Huygens Mission is given, followed by a general description of navigation. Orbit control and maneuver execution methods are defined, along with an outline of the orbit control staffing and operations philosophy. Finally, an example schedule of orbit control operations is shown.

navigation↗
NASA NTRS1986

ICE navigation support

The International Cometary Explorer (ICE) encounter with Comet Giacobini-Zinner took place 7 years after the spacecraft's original launch on 12 August 1978 as the International Sun Earth Explorer 3 (ISEE-3), part of a three-spacecraft project to study the interaction between the solar wind and the Earth's magnetosphere. Transfer to an interplanetary trajectory was performed via a 119-km-altitute, gravity-assist, lunar swingby on December 1983. Navigation support during interplanetary cruise and comet encounter was provided by orbit determination utilizing radio metric data from the DSN 64-meter antennas in Goldstone, California and Madrid, Spain. Orbit solutions yielding predictions of 50-km geocentric delivery accuracy in the target aim plane were achieved during interplanetary cruise and at comet encounter using 6-to-12-week data arcs between periodic attitude-change maneuvers. One-sigma two-way range and range rate residuals were consistently 40 meters and 0.2 mm/s or better, respectively. Non-gravitational forces affected the comet's motion during late August and early September 1985 and caused a 2300-km shift in the orbit of the comet relative to the spacecraft. This necessitated a final ICE orbit trim maneuver 3 days prior to encounter. Near-real-time assessment of two-way 2-GHz (S-band) Doppler pseudo-residuals during the June and July 1985 trajectory change maneuvers aided in calibration of the spacecraft's thrusters in preparation for this final critical maneuver. Post-flight analysis indicates tail centerline passage was achieved within 10 seconds of the predicted time and geocentric position uncertainty at encounter was less than 40 km.

Efron, L.↗
NASA NTRS1980

A long-life bipropellant system demonstration: Viking Orbiter Propulsion System - 4 years in space and operating

On April 23, 1980, Viking Orbiter One (VO-1), operating in the blowdown mode, completed a ten second Mars orbit trim maneuver to position the spacecraft for its final science sequence in May-June 1980. This brought the number of propulsive maneuvers for VO-1 to 23. Total accumulated operating time for the rocket engine was 2896 seconds, representing a total impulse of 3.93 x 10 to the 6th N-sec. The estimated propellant remaining was sufficient to operate the rocket engine for an additional 30 seconds. VO-1 has completed more than 1700 days in space, 1400 days in orbit around Mars and more than two years of attitude control system operation with helium gas transferred from the propulsion system pressurant tank. The mass of helium remaining is expected to be sufficient for attitude control through June 1980. This paper presents the flight history of the Viking 75 Orbiter Propulsion Systems and summarizes the design and test philosophy which have contributed to their success.

Schmit, D. D.↗