Flyby Trajectories Research Articles

Trajectory optimization of near-Earth asteroids exploration by using reusable probes from cislunar space

Implementing the flyby to Near-Earth Asteroids (NEAs) with the potential impact risks to the Earth allows for obtaining detailed physical parameters, thereby supporting the high-precision orbit prediction and planetary defense strategy. Different from those conducted asteroid flyby missions, in the 12th China Trajectory Optimization Competition (CTOC-12), a NEAs flyby trajectory design problem using reusable probes that depart from a Lunar Distant Retrograde Orbit (DRO) station in the cislunar space was released. The objective was flyby to as many NEAs as possible using up to 20 probes within a total of 10 years. The ∑ team proposed a solution that can explore 47 NEAs using 11 probes, ranking the first in the competition. In this paper, the methods and results from the winning team are introduced, including mission analysis and preliminary design, and low-energy transfer trajectory optimization. In particular, a round-trip trajectory is divided into three phases: deep space transfer, indirect transfer between the Earth to DRO, and DRO phasing and rendezvous. With the combination of global optimization and local optimization algorithms, the required velocity increments to change the orbital planes are effectively reduced, thus increasing the number of the explored NEAs. The final solution of our team is presented and the results are compared with those of the top three teams. The competition demonstrates that the regularization of flyby missions from the cislunar space to explore NEAs with the potential impact risks to the Earth is the feasible and promising.

Structure and dynamics of the Hermean magnetosphere revealed by electron observations from the Mercury electron analyzer after the first three Mercury flybys of BepiColombo

The Mercury electron analyzer (MEA) obtained new electron observations during the first three Mercury flybys by BepiColombo on October 1, 2021 (MFB1), June 23, 2022 (MFB2), and June 19, 2023 (MFB3). BepiColombo entered the dusk side magnetotail from the flank magnetosheath in the northern hemisphere, crossed the Mercury solar orbital equator around midnight in the magnetotail, traveled from midnight to dawn in the southern hemisphere near the closest approach, and exited from the post-dawn magnetosphere into the dayside magnetosheath. We aim to identify the magnetospheric boundaries and describe the structure and dynamics of the electron populations observed in the various regions explored along the flyby trajectories. We derive 4s time resolution electron densities and temperatures from MEA observations. We compare and contrast our new BepiColombo electron observations with those obtained from the Mariner 10 scanning electron spectrometer (SES) 49 years ago. A comparison to the averaged magnetospheric boundary crossings of MESSENGER indicates that the magnetosphere of Mercury was compressed during MFB1, close to its average state during MFB2, and highly compressed during MFB3. Our new MEA observations reveal the presence of a wake effect very close behind Mercury when BepiColombo entered the shadow region, a significant dusk-dawn asymmetry in electron fluxes in the nightside magnetosphere, and strongly fluctuating electrons with energies above 100s eV in the dawnside magnetosphere. Magnetospheric electron densities and temperatures are in the range of 10-30 cm$^ $ and above a few 100s eV in the pre-midnight-sector, and in the range of 1-100 cm$^ $ and well below 100 eV in the post-midnight sector, respectively. The MEA electron observations of different solar wind properties encountered during the first three Mercury flybys reveal the highly dynamic response and variability of the solar wind-magnetosphere interactions at Mercury. A good match is found between the electron plasma parameters derived by MEA in the various regions of the Hermean environment and similar ones derived in a few cases from other instruments on board BepiColombo.

Multiple SSO Space Debris Flyby Trajectory Design Based on Cislunar Orbit

This paper investigates the trajectory design problem in the scenario of a multiple Sun-synchronous Orbit (SSO) space debris flyby mission from a DRO space station. At first, the characteristics of non-planar transfer from DRO to SSO in the Earth–Moon system are analyzed. The methods of large-scale ergodicity and pruning are utilized to investigate single-impulse and two-impulse DRO–Earth transfers. Using a powered lunar flyby, the two-impulse DRO–Earth transfer is able to fly by SSO debris while satisfying the requirements of the mission. After the local optimization, the optimal result of two-impulse DRO–Earth transfer and flyby is obtained. A multi-objective evolutionary algorithm is used to design the Pareto-optimal trajectories of multiple flybys. The semi-analytical optimization method is developed to provide the estimations of the transfer parameters in order to reduce the computations caused by the evolutionary algorithm. Simulations show that transferring from the 3:2 resonant DRO to a near-coplanar flyby of a SSO target debris using a powered lunar gravity assist needs a 0.47 km/s velocity increment. The mission’s total velocity increment is 1.39 km/s, and the total transfer time is 2.23 years.

Design of Flyby Trajectories with Powered Gravity and Aerogravity Assist Maneuvers

In this paper, we investigate flyby trajectories combining powered gravity assist (PGA) with aerogravity assist (AGA) in the planar elliptic restricted three-body problem (PERTBP). The patched flyby trajectory is divided into three portions: the PGA, AGA and ballistic portions, successively. In the PGA portion, continuous thrusts are conducted to change the speed and drive the altitude of a vehicle below the atmosphere edge. A simple flight-path angle guidance algorithm for three stages is used to design the orbit in the AGA portion. Taking the Sun–Mars PERTBP system as an example, flyby trajectories around Mars combining PGA with AGA are constructed and discussed in detail. In addition, numerical results show that the elliptical effect of the model should not be ignored, and it is necessary to investigate patched flyby orbits in the PERTBP.

B-Plane Resonant Flybys: Theory Extension to Elliptical Orbits and Dynamic Programming Application

A convenient formalism for the design of resonant flyby trajectories is the B-plane, where postencounter orbits with target resonance conditions or semimajor axes can be analytically mapped. This framework has been developed by many authors starting from the classical Öpik’s theory for close encounters, but it still relies on the approximation of circular orbits of the flyby bodies. In this work, the theory is analytically extended to account for elliptical planetary orbits. The classical and the extended formulations are tested and compared on two mission design applications, showing nonnegligible differences when the flyby body has a marked eccentricity. Further validation using a full three-body model confirmed the greater accuracy of the extended formulation. The second part of the paper proposes an efficient dynamic programming approach to the design of unperturbed resonant flybys. This problem has traditionally been addressed within broader optimization frameworks involving generic multiple gravity assists. However, focusing only on the resonant sequence allows the problem to feature a convenient structure for the implementation of dynamic programming. The developed algorithm is tested by reproducing the design of Solar Orbiter’s resonant phase with Venus, used in the actual mission to gradually raise the ecliptic inclination and reduce the distance at perihelion.

Study of Small Bodies of the Solar System: Odyssey-Asteroids Project

The paper discusses priority scientific tasks related to the study of small bodies in the Solar System, identifies the most promising objects for investigation from a spacecraft on a flyby trajectory and the sample return mission, and develops proposals for the preliminary composition of scientific instruments for remote asteroid research methods. A long-term and phased Russian scientific program for studying small Solar System bodies using spacecraft with electric propulsion has been proposed. The project is designed in such a way as to explore the largest number of scientifically interesting asteroids using a smaller number of spacecraft. A design concept for a small spacecraft to investigate near-Earth asteroids on a flyby trajectory and a main spacecraft for studying metallic asteroids in the Main Belt and sample sample return has been developed. A ballistic analysis of the flyby of five near-Earth asteroids and three metallic asteroids in the Main Belt is presented, as well as a ballistic analysis of the sample return mission from a Main Belt asteroid. The option of sample return using the nuclear tug Zevs is also considered.

The Influence of Field-Aligned Currents on Electron Density in the Ionosphere: Combined Observations of SWARM Satellites and ESR Radar

The results are presented of combined measurements by the SWARM spacecraft (SC) and European incoherent scatter radar on Svalbard for two events of simultaneous observations: in the nighttime ionosphere during substorm activation on January 9, 2014, and in the daytime ionosphere under quiet conditions on February 5, 2017. Onboard magnetometers of the SWARM SC provide measurements of field-aligned current density over the ionosphere. The radar, which is under the flyby trajectory at this time, measures the vertical distribution of the electron density (Ne). Experiments have shown that, under disturbed nighttime conditions, at the location of the field-aligned current flowing from the ionosphere, the plasma density increases throughout the entire slab of the ionosphere and the change in Ne is in agreement with theoretical estimates. In the daytime quiet ionosphere, Ne increases only in the F layer, but practically does not change in the E layer. The differences may be due to the fact that, in the first case, the carriers of the upward directed current are represented by the entire energy spectrum of auroral electrons of 1–10 keV, and in the second case only by the low-energy part.

A 3‐D Shape Reconstruction Strategy for Small Solar System Bodies With Single Flyby Spaceborne Radar

AbstractThis article presents a novel 3‐D shape reconstruction strategy for small solar system bodies using spaceborne radar which is applied in flyby trajectories to characterize multiple targets in one mission to save time and cost. In this study, we establish a measurement geometry for rapidly spinning small solar system bodies that combines the motion properties of synthetic aperture radar and circular synthetic aperture radar techniques. We also propose a modified imaging algorithm, which is processed using Cardano's formula and the modified polar format algorithm, to improve the imaging quality. Finally, we present simulated results of point‐scattering and 3D shape models. Our analysis shows that the shape reconstruction errors of the algorithm are less than 1.5 m as indicated by the standard deviation.

Построение траектории малого космического аппарата для облета базового космического аппарата с целью наружного осмотра и оценка энергетических затрат на маневр облета

The paper presents a methodology for constructing a flyby trajectory of a base spacecraft for the purpose of inspecting it using a small spacecraft carried on board and estimating the required characteristic velocity reserves for the flyby maneuver. The use of approximate calculation methods made it possible to obtain the simplest dependences of trajectory parameters with high accuracy. The technique allows not only to estimate the energy costs for orbital maneuvers, but also allows one to calculate the values of control impulses for the real problem of controlling the motion of a small spacecraft relative to the base spacecraft.

3D Radiative-transfer Simulations of the Ejecta Plume Anticipated from DART Impact

We present a modeling approach that allows the reconstruction of detailed images of the ejecta plume produced by the DART impact on asteroid Dimorphos. The approach is based on the 3D radiative-transfer technique and uses the publicly available HYPERION software package. The modeling automatically includes all interactions of light with the asteroid and ejecta plume, including transmission of the light through a hollow cone, reflection from the asteroid, and second transmission through the ejecta for each point within the ejecta plume and asteroid surface. The results of the modeling are the FITS images of the asteroid and ejecta as they will be seen by the LEIA camera on board LICIACube for any specific moments after impact. The parameters of the modeling are preimpact assumptions regarding Dimorphos’ shape and composition, the presumed impact location, and the planned flyby trajectory of LICIACube. The results of the modeling show the readiness of our modeling tools to simulate the realistic ejecta plume after impact with the purpose to model the LICIACube images at different moments after impact and estimate the properties of the dust ejecta particles and the ejecta mass.

Determining the dust environment of an unknown comet for a spacecraft flyby: The case of ESA’s Comet Interceptor mission

Context.An assessment of the dust environment of a comet is needed for data analysis and planning spacecraft missions, such as ESA’s Comet Interceptor (CI) mission. The distinctive feature of CI is that the target object will be defined shortly before (or even after) launch; as a result, the properties of the nucleus and dust environment are poorly constrained, and therefore make the assessment of the dust environment challenging.Aims.The main goal of the work is to provide realistic estimations of a dust environment based on very general parameters of possible target objects.Methods.Contemporary numerical models of a dusty-gas coma were used to obtain spatial distribution of dust for a given set of parameters. By varying parameters within a range of possible values, we obtained an ensemble of possible dust distributions. Then, this ensemble was statistically evaluated in order to define the most probable cases and hence reduce the dispersion. This ensemble can not only be used to estimate the likely dust abundance along a flyby trajectory of a spacecraft, for example, but also to quantify the associated uncertainty.Results.We present a methodology of the dust environment assessment for the case when the target comet is not known beforehand (or when its parameters are known with large uncertainty). We provide an assessment of dust environment for the CI mission. We find that the lack of knowledge of any particular comet results in very large uncertainties (~3 orders of magnitude) for the dust densities within the coma. The most sensitive parameters affecting the dust densities are the dust size distribution, the dust production rate, and coma brightness, often quantified by Afρ. Further, the conversion of a coma’s brightness (Afρ) to a dust production rate is poorly constrained. The dust production rate can only be estimated down to an uncertainty of ~0.5 orders of magnitude if the dust size distribution is known in addition to the Afρ.Conclusions.To accurately predict the dust environment of a poorly known comet, a statistical approach needs to be taken to properly reflect the uncertainties. This can be done by calculating an ensemble of comae covering all possible combinations within parameter space as shown in this work.

GTOC 11: Results found at Beijing Institute of Technology and China Academy of Space Technology

This paper presents the crucial method for the results found at Beijing Institute of Technology and China Academy of Space Technology in the 11th Global Trajectory Optimization Competition (GTOC-11). To build 12 solar-power stations placed in the “Dyson Ring” orbit around the Sun, GTOC-11 focuses on the flyby trajectory design, low-thrust trajectory optimization, and target assignment problem. The mission with time and state constraints causes many difficulties in the design and optimization, which is performed in the following four steps. The first step is to design the orbital elements of the “Dyson Ring” by the grid search method. An approximate model is utilized to evaluate the minimum transfer time for each candidate at first, and the accurate solutions are obtained by the indirect method. The second step involves the Mother Ship trajectories design. A large quantity of earth-to-asteroid and asteroid-to-asteroid subsequences are generated by parallel beam search. The complete trajectories of Mother Ship are designed by connecting the subsequences using beam search. The third step involves the station assignment problem, which is required to design the asteroid transfer device activation epoch and the target station assignment. Based on the results above, the last step involves the rendezvous trajectories optimization to obtain the accurate thrust direction profile. Finally, the submitted and post-competition results are reported.

GTOC 11: Results from Tsinghua University and Shanghai Institute of Satellite Engineering

In this paper, the methods and results from Tsinghua University and Shanghai Institute of Satellite Engineering for the 11th Global Trajectory Optimization Competition (GTOC11) are presented. To deal with the complicated “Dyson Sphere” building problem, a three-stage procedure is conducted. First, the pre-analysis is performed to reduce search space. It is found that two-impulse maneuvers between asteroid flybys are near-optimal, the semi-major axis of the “Dyson Ring” should be better at 1.0–1.5 AU, and the larger arrival mass asteroids tend to be selected. Second, the globally optimal trajectory design problem is further divided into two sub-problems, the mothership trajectory design and the asteroid assignment to the “Dyson Ring” power stations. For the first problem, beam search is used to obtain numerous single mothership trajectories based on a pre-constructed flyby trajectory database of 3–8 asteroids. The overall trajectories and asteroids visited are obtained by selecting 10 mothership trajectories with a genetic algorithm. For the second problem, we build a database of optimal rendezvous times for all the 83,453 asteroids at different phase angles to reach power stations of different radii and phase angles, then a greedy algorithm is proposed to obtain the asteroid arrival schedule based on all the asteroids visited by motherships. Finally, local optimization of asteroid sequence and flyby epochs is conducted. The activation time adjustment in combination with indirect continuous-thrust trajectory optimization is used based on the global optimization result. In the final submission, motherships fly by 388 asteroids, and the minimum mass of twelve power stations reaches 94% of the theoretical upper bound, which is defined using the minimum-time orbital transfers with free initial and target phases.

Robust Space Trajectory Design Using Belief Optimal Control

This paper presents a novel approach to the robust solution of optimal impulsive control problems under aleatory and epistemic uncertainty. The novel approach uses belief Markov decision processes to reformulate the control problem in terms of uncertainty distributions, called beliefs, rather than the realizations of the system states. This formulation leads to the definition of a belief optimal control problem where the cost function and constraints are functions of the uncertainty distributions. The control formulation encompasses orbit determination arcs as well. The belief optimization is solved with a shooting-like transcription and a nonlinear programming solver to optimize the resulting discretized problem. Both aleatory and epistemic uncertainties are propagated with a nonintrusive polynomial expansion to capture the nonlinearities of the dynamics. Finally, this new approach is applied to the robust optimization of a flyby trajectory of the Europa Clipper mission in a scenario characterized by knowledge, execution, and observation uncertainty.

Assessing JUICE's ability of in situ plume detection in Europa's atmosphere

ESA's upcoming JUpiter Icy moons Explorer (JUICE) is scheduled to perform two flybys of Jupiter's moon Europa. Here, we present the results of our investigation into JUICE's capability to detect plumes and to separate them from the background water in the atmosphere as a function of their source's location and mass flux on the Europan surface using the neutral mass spectrometer NIM. For both of the currently planned flybys we evaluate different scenarios to estimate how feasible such a detection is, using a Monte Carlo particle tracing model of a plume. We also incorporate the putative plume candidates reported by Roth et al. (2014b), Sparks et al. (2016), Sparks et al. (2017), Jia et al. (2018), Arnold et al. (2019) and Sparks et al. (2019) into this investigation. We come to the conclusion that the first flyby trajectory is better suited to detect the potential plume candidates listed above as they are detectable down to mass fluxes of approx. 100 ​kg/s. The second flyby requires mass fluxes between 100 ​kg/s and 500 ​kg/s for all suggested plume candidates to be detectable. This discrepancy is caused by the first flyby's closer proximity to the locations of the suggested plume sources which lie mainly on the southern hemisphere. Separation of water plumes from the atmospheric water vapour density is dependent on the mass flux of the respective plume source. The only plume separable from the background water in the atmosphere at the lowest investigated plume source mass flux of 1 ​kg/s is the one suggested by Roth et al. (2014b). It is therefore the most likely plume to be detected by JUICE. Furthermore, we investigate the detectability of trace gas contents in a plume and analyse how these impact upon plume detection. The spacecraft will be able to detect whether lighter-than-water trace gas species are present within the plume down to trace gas source mass fluxes of 0.1 ​kg/s. Provided this is the case, such species constitute a means to identifying plumes in the Europan atmosphere. Finally, the effects of lowering the flyby altitude are examined. We find that lowering the altitude of the CA does not increase the region of separability. Therefore, lowering the second flyby trajectory will not suffice for the spacecraft to be able to identify plumes that originate from the locations of the candidates mentioned above. Considering that the second flyby is the most likely to be lowered, this case study provides an example of the importance of arranging the second trajectory in a manner such that its ground track lies in close proximity to the locations of the suggested plume candidates listed above. This approach to the mission planning maximises the chance of separating the presumptive plumes from the atmospheric background water even at the lowest plume source mass fluxes.

Flyby reaction trajectories: Chemical dynamics under extrinsic force.

Dynamic effects are an important determinant of chemical reactivity and selectivity, but the deliberate manipulation of atomic motions during a chemical transformation is not straightforward. Here, we demonstrate that extrinsic force exerted upon cyclobutanes by stretching pendant polymer chains influences product selectivity through force-imparted nonstatistical dynamic effects on the stepwise ring-opening reaction. The high product stereoselectivity is quantified by carbon-13 labeling and shown to depend on external force, reactant stereochemistry, and intermediate stability. Computational modeling and simulations show that, besides altering energy barriers, the mechanical force activates reactive intramolecular motions nonstatistically, setting up "flyby trajectories" that advance directly to product without isomerization excursions. A mechanistic model incorporating nonstatistical dynamic effects accounts for isomer-dependent mechanochemical stereoselectivity.

LICIACube - The Light Italian Cubesat for Imaging of Asteroids In support of the NASA DART mission towards asteroid (65803) Didymos

“LICIACube – the Light Italian Cubesat for Imaging of Asteroids” is managed by the Italian Space Agency (ASI) and will be part of the NASA DART mission, with the aim of i) documenting the DART impact’s effects on the secondary member of the (65803) Didymos binary asteroid system, ii) characterizing the shape of the target, and iii) performing dedicated scientific investigations on it. DART probe will be launched at the end of 2021 and LICIACube will be hosted as piggyback during the interplanetary cruise, then released 10 days before the impact, and autonomously guided along its fly-by trajectory. The LICIACube payload is composed by LEIA, a narrow FoV camera, and LUKE, a wide FoV imager with an RGB Bayer pattern filter, that will collect and transmit to Earth several unique images of the effects of the DART impact on the asteroid, such as the formation and the development of the plume potentially determined by the impact.LICIACube will be the first deep space mission developed and autonomously managed by an Italian team: the design, integration and test of the CubeSat have been assigned by ASI to the aerospace company Argotec, while the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Center, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center. The LICIACube team includes a wide Italian scientific community, involved in the definition of all the aspects of the mission: trajectory design; mission definition (and real-time orbit determination during operations); impact, plume and imaging simulation and modelling, in preparation of a suitable framework for the analysis and interpretation of in-situ data. The major technological mission challenge, i.e. the autonomous targeting and imaging of such a small body during a fast fly-by, to be accomplished with the limited resources of a CubeSat, is affordable thanks to a strong synergy of all the mentioned teams in support of the engineering tasks.

Delay Doppler SAR Focusing and Quantitative Quality Control of the Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON) Sounding Data Product

Synthetic aperture radar (SAR) focusing will be a fundamental step in the analysis of the radar sounding datasets collected by the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) instrument as part of NASA's upcoming Europa Clipper mission. Due to the flyby trajectory of the mission, REASON data acquisition will be distinct compared to other space-borne radar sounders, and therefore, require a tailored SAR focusing strategy. Here, we present a SAR focusing architecture based on the delay Doppler approach employed in US SHAllow RADar (SHARAD) data analysis with the following modifications for REASON data idiosyncrasies; an interpolation to a constant ground track interval to account for REASON's variable PRF; and an adaptive Doppler centroid estimation to account for the flyby geometry. The ability of our modified delay Doppler SAR focusing approach to focus space-borne datasets as well as its specific feasibility for REASON are demonstrated using both SHARAD and MARSIS datasets. In addition, we present a quantitative quality control framework based on pixel power probabilities and demonstrate how it can be leveraged to quantify the effects of SAR focusing and differentiate focused results generated with different processing parameters. Finally, we revisit and discuss the assumption of depth-independent SAR focusing implicit in the choice to construct a REASON SAR focusing approach based on the delay Doppler method and provide a comparison with depth-dependent SAR focusing for a simplified acquisition geometry.

Anomalous Sun Flyby of 1I/2017 U1 (`Oumuamua)

The findings of Micheli et al. (Nature2018, 559, 223–226) that 1I/2017 U1 (`Oumuamua) showed anomalous orbital accelerations have motivated us to apply an impact model of gravity in search for an explanation. A small deviation from the 1/r potential, where r is the heliocentric distance, is expected for the gravitational interaction of extended bodies as a consequence of this model. This modification of the potential results from an offset of the effective gravitational centre from the geometric centre of a spherically symmetric body. Applied to anomalous Earth flybys, the model accounts for energy gains relative to an exact Kepler orbit and an increased speed of several spacecraft. In addition, the flat rotation profiles of eight disk galaxies could be explained, as well as the anomalous perihelion advances of the inner planets and the asteroid Icarus. The solution in the case of `Oumuamua is also based on the proposal that the offset leads to an approach and flyby trajectory different from a Kepler orbit without postulating cometary activity. As a consequence, an adjustment of the potential and centrifugal orbital energies can be envisaged outside the narrow uncertainty ranges of the published post-perihelion data without a need to re-analyse the original data. The observed anomalous acceleration has been modelled with respect to the orbit solutions JPL 16 and “Pseudo-MPEC” for 1I/`Oumuamua.

A comprehensive study of Titan’s magnetic pile-up region during the Cassini era

While Saturn’s largest moon Titan is devoid of an intrinsic magnetic field, draping of the giant planet’s magnetospheric field around Titan’s ionosphere generates a pile-up region at the moon’s ramside. In this study, we analyze Cassini magnetic field data from all 126 Titan flybys to systematically characterize the extensions and magnitudes of the field enhancements at its ramside. Along each flyby trajectory, the segments where Cassini crossed the piled-up magnetic field are determined, and altitude profiles of the pile-up strength are also generated. We investigate the dependency of the extension and strength of the pile-up region on various parameters, such as the Saturn local time and the magnetospheric environment to which Titan is exposed. In this way, we generate a comprehensive picture of Titan’s ramside magnetic pile-up region during the Cassini era. Our major findings are: (1) The extensions of the observed pile-up reveal an asymmetry between the Saturn-facing and Saturn-averted sides caused by the large gyro-radii of ionospheric pick-up ions. (2) The observed pile-up radial extensions are nearly independent of Titan’s orbital position. (3) The lower boundary of the pile-up region is located at an altitude of 0.35 Titan radius, denoting the average altitude of the magnetic ionopause. (4) Considering the error bars, the altitude profiles of the pile-up strength show a stable picture, i.e., the radial profile of the field magnitude is independent of Saturn’s magnetospheric environment and local time.