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The aster mission: Exploring for the first time a triple system asteroid

Authors:
Elbert E N Macau at Universidade Federal de São Paulo
Elbert E N Macau
O. C. Winter at São Paulo State University
O. C. Winter
Haroldo Fraga de Campos Velho at National Institute for Space Research, Brazil
Haroldo Fraga de Campos Velho
Alexander A. Sukhanov at National Institute for Space Research, Brazil
Alexander A. Sukhanov
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Abstract

2001 SN263 is a triple system asteroid. Although it was discovery in 2001, in 2008 astronomical observation carried out by Arecibo observatory revealed that it is actually a system with three bodies orbiting each other. The main central body is an irregular object with a diameter about 2.8 km, while the other two are small objects with less than 1 km across. This system presents an orbital eccentricity of 0.47, with perihelion of 1.04 and aphelion of 1.99, which means that it can be considered as a Near Earth Object. This interesting system was chosen as the target for the Aster mission - first Brazilian space exploration undertaking. A small spacecraft with 150 kg of total mass, 30 kg of payload with 110 W available for the instruments, is scheduled to be launched in 2015, and in 2018 it will approach and will be put in orbit of the triple system. This spacecraft will use electric propulsion and in its payload it will carry image camera, laser rangefinder, infrared spectrometer, mass spectrometer, and experiments to be performed in its way to the asteroid. This mission represents a great challenge for the Brazilian space program. It is being structured to allow the full engagement of the Brazilian universities and technological companies in all the necessary developments to be carried out. In this paper, we present some aspects of this mission, including the transfer trajectories to be used, and details of buss and payload subsystems that are being developed and will be used. Copyright ©2010 by the International Astronautical Federation. All rights reserved.
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1/29/2016 IAC Archive — IAC-11/B4/2/7
http://www.iafastro.net/iac/archive/browse/IAC-11/B4/2/10263/ 1/1
THEASTERMISSION:EXPLORINGFORTHEFIRSTTIMEATRIPLE
SYSTEMASTEROID
Papernumber
IAC‐11,B4,2,7,x10263
Author
Prof.ElbertE.N.Macau,InstitutoNacionaldePesquisasEspaciais(INPE),Brazil
Coauthor
Prof.OthonWinter,UNESP‐UnivEstadualPaulista,Brazil
Coauthor
Mr.HaroldoFragadeCamposVelho,NationalInstituteforSpaceResearch‐INPE,Brazil
Year
2011
Abstract
2001SN263isatriplesystemasteroid.Althoughitwasdiscoveryin2001,in2008astronomicalobservationcarried
outbyAreciboobservatoryrevealedthatitisactuallyasystemwiththreebodiesorbitingeachother.Themain
centralbodyisanirregularobjectwithadiameterabout2.8km,whiletheothertwoaresmallobjectswithlessthan
1kmacross.Thissystempresentsanorbitaleccentricityof0.47,withperihelionof1.04andaphelionof1.99,which
meansthatitcanbeconsideredasaNearEarthObject.Thisinterestingsystemwaschosenasthetargetforthe
AstermissionfirstBrazilianspaceexplorationundertaking.Asmallspacecraftwith150kgoftotalmass,30kgof
payloadwith110Wavailablefortheinstruments,isscheduledtobelaunchedin2015,andin2018itwillapproach
andwillbeputinorbitofthetriplesystem.Thisspacecraftwilluseelectricpropulsionandinitspayloaditwillcarry
imagecamera,laserrangefinder,infraredspectrometer,massspectrometer,andexperimentstobeperformedinits
waytotheasteroid.ThismissionrepresentsagreatchallengefortheBrazilianspaceprogram.Itisbeingstructured
toallowthefullengagementoftheBrazilianuniversitiesandtechnologicalcompaniesinallthenecessary
developmentstobecarriedout.Inthispaper,wepresentthetechnologicalaspectsofthismission,includingthe
transfertrajectoriestobeused,andthebussandpayloadsubsystemsthatarebeingdevelopedandwillbeused.
Also,wediscusstheexpectedscientificandtechnologicalconsequencesthatareexpectedfortheAstermission.
Abstractdocument
IAC‐11,B4,2,7,x10263.brief.pdf
Manuscriptdocument
Togetthemanuscript,pleasecontactIAFSecretariat
... Under these assumptions, the low-thrust trajectory is spiral with instantaneous orbits close to circular ones at any time of the transfer. The mass flow rate can be found for the parameters given in Table 2 as follows (Macau et al. 2010 ...
... where F and I sp are thrust and specific impulse, g = 9.80665 m/s 2 is acceleration of free fall. Then the spacecraft mass m, transfer time t, and number of orbits N versus radius of the final orbit can be calculated using the following equations (see Macau et al. 2010): ...
... where m 0 is initial spacecraft mass, v 0 and v are velocities in the initial and final circular orbits, μ = 3,98,600.45 km 3 /s 2 is the Earth gravitational parameter, integral L 3 = t 0 (v 0 /I sp g + ln t)dt is calculated in Macau et al. (2010) and Marchis et al. (2007). Figures 14, 15 and 16 show the m, t, and N values respectively versus radius of the final orbit for the three electric propulsion cases given in Table 2. ...
Permanent magnet Hall thruster development for future Brazilian space missions
Article
  • Dec 2015
Electric propulsion is now a successful method for primary and secondary propulsion of deep space long-duration missions and for geosynchronous satellite attitude control. The Plasma Physics Laboratory of UnB has been developing a permanent magnet Hall thruster (PHALL) for the UNIESPAÇO program, part of the Brazilian space activities program (PNAE) since 2004. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the plasma channel of the thruster is very significant. It allows the development of a Hall thruster with power consumption low enough to be used in small- and medium-size satellites. The PHALL project consists on plasma source design, construction and characterization of the Hall-type propulsion engine using several plasma diagnostics sensors. PHALL is based on a plasma source in which a Hall current is generated inside a cylindrical channel with an axial electric field produced by a ring anode and a radial magnetic field produced by permanent magnets. In this work, a brief description of the plasma propulsion engine, its diagnostics instrumentation and measured plasma parameters with a focus for possible applications of PHALL on orbit transfer maneuvering for future Brazilian geostationary satellite space missions is shown. More specifically, we will show plasma density and temperature space profiles inside and outside the thruster channel, ion temperature measurements based on Doppler broadening of spectral lines and ion energy measurements. Based on the measured plasma parameters we construct an aptitude figure of the PHALL. It contains the specific impulse, total thrust, propellant flow rate and power consumption necessary for orbit raising of satellites. Based on previous studies of geosynchronous satellite orbit positioning we perform numerical simulations of satellite orbit raising from an altitude of 700–36,000 km using a PHALL operating in the 100–500 mN thrust range. To perform these calculations integration techniques were used. The main simulation parameters were orbit raising time, fuel mass, total satellite mass, thrust and exhaust velocity. We conclude by comparing our results with results obtained with known space missions performed with Hall thrusters.
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... In this window, in terms of exploration conditions, the Sun-s/c-Earth angle keeps inside the range [55°, 27°], and the distances from the s/c to the Sun and to the Earth are, respectively, [150,270] x 10 6 km and [150,190] x 10 6 km. More details involving the first Brazilian deep space mission ASTER can be found in the works of Araujo et al. (2012), Macau et al. (2011), Perna et al. (2014), and Sukhanov et al. (2010). ...
... Attitude control is an important issue in the scheme devised and presented, which assumes the Sun-pointing condition is acquired and maintained while the 1-month campaign happens (in this case, the total variation of the pointing vector is small, about 28°). This attitude approach depends on the attitude control system on board the s/c, composed by a sun sensor, star trackers and reaction wheels (Macau et al., 2011). These systems are, in general, very stable and precise (order of arc seconds). ...
Encounter trajectories for deep space mission ASTER to the triple near Earth asteroid 2001-SN263. The laser altimeter (ALR) point of view
Article
  • Jan 2021
  • ADV SPACE RES
In cooperation with Russia, the Brazilian deep space mission ASTER plans to send a small spacecraft to investigate the triple asteroid 2001-SN263. The nearest launch opportunities for this project include June 2022 and June 2025. One main exploration campaign is being planned with focus on the largest asteroid (Alpha). Among the instruments under development, a laser altimeter (named ALR) was preliminarily designed and presented in 2010–2011. Many studies to define mission and instruments requirements were performed aiming at the characterization of important issues for the successful realization of the mission. Among them, the identification of a suitable trajectory that could be followed by the ASTER spacecraft in the encounter phase, when the main campaign will take place. This paper describes the effort undertaken with focus on the laser altimeter operation. Possible encounter trajectories were modelled and simulated to identify suitable approach parameters and conditions allowing the accomplishment of the intended investigation. The simulation also involves the instrument operation, considering approach geometry, attitude, relative motion, time/date, and the dynamics of the main asteroid. From the laser altimeter point of view, keeping in mind the desired coverage results (50% minimum surface coverage of asteroid Alpha, complying with horizontal and vertical resolution requirements), results point out crucial features for the encounter trajectory, like the need for a small inclination (10⁻⁶ degrees; with respect to the asteroid's orbit), the most favourable spacecraft positioning (between the Sun and the asteroid) and pointing condition (back to the Sun), the minimum amount of achievable surface coverage (58%, focused on central areas), and the most proper time to conduct the main campaign (January 2025). Concerning the instrument, results offer refined values for divergence angle (500 to 650 μrad, half-cone), pulse repetition frequencies (from 1/20 to 1 Hz), and consequent data generation rates. A simulation tool that can use any 3D generated trajectories as input data was created for the analyses presented here. Although created for the ALR in this mission, this simple analysis tool can be adapted to other instruments in this or other missions.
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... This study is useful for understanding the dynamical behaviors of massless particles in the triple asteroid system. In addition, triple asteroid systems are the target of future missions (Macau et al. 2011). The study of the dynamical environment around the triple asteroid system 87 Sylvia will help to design the trajectories for the spacecraft of future missions. ...
Dynamical Environment in the Triple Asteroid System 87 Sylvia
Article
Full-text available
  • Apr 2019
  • ASTROPHYS SPACE SCI
We investigate the dynamical environment in the first announced triple asteroid system 87 Sylvia. The 3D shape of the primary is rebuilt from shape data using the polyhedral model method. The dynamical characteristics of the primary, such as the surface height, the surface effective potential, the surface gravitational acceleration, the structure of the zero-velocity surfaces, and the locations and stability of the equilibrium points, have been investigated. Five equilibrium points are in the potential of 87 Sylvia. Both unstable periodic orbits and stable periodic orbits coexist near the surface of the primary of the triple asteroid system 87 Sylvia. Under the full perturbation force of two moonlets, the semi-major axis, the eccentricity, the inclination, and the mechanical energy vary periodically and have no secular terms. Among them, the semi-major axis, the eccentricity, and the mechanical energy have two period terms, namely, a long period term and a short period term; the inclination has three period terms, i.e., a long period term, a short period term, and an intermediate period term. Unlike these orbital parameters, the argument of the pericenter and the longitude of the ascending node have a secular term, a long period term and a short period term. A simulation of the trajectories of 1000 grains generated in the system considering the gravity of the irregular shape and two moonlets of the primary has been presented. The grains may impact on the surface of the primary, escape the system, or move in the system.
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... Some other researches considered general trajectories around smaller bodies, which can be used in mission design of future missions to asteroids, like Werner, 1994;Rossi et al., 1999;Scheeres, 1994Scheeres, , 2012ac; Scheeres and Hu, 2001;Bartczakk et al., 2006;Byram and Scheeres, 2009; Venditti and Prado, 2014. The present research is related to the mission named ASTER, that has some preliminary studies available in the literature ( Sukhanov et al., 2010;Macau et al. 2010). Its main objective is to study the triple NEA 2001SN 263 ( Araújo et al., 2012;, b), because it is believed that it contains information about the original composition of the Solar System. ...
Developing the “Precessing Inclined Bi-Elliptical Four-Body Problem with Radiation Pressure” to Search for Orbits in the Triple Asteroid 2001SN263
Article
Full-text available
  • Dec 2015
  • ADV SPACE RES
Space missions to visit small bodies of the Solar System are important steps to improve our knowledge of the Solar System. Usually those bodies do not have well known characteristics, as their gravity field, which make the mission planning a difficult task. The present paper has the goal of studying orbits around the triple asteroid 2001SN263, a Near-Earth Asteroid (NEA). A mission to this system allows the exploration of three bodies in the same trip. The distances reached by the spacecraft from those three bodies have fundamental importance in the quality of their observations. Therefore, the present research has two main goals: (i) to develop a semi-analytical mathematical model, which is simple, but able to represent the main characteristics of that system; (ii) to use this model to find orbits for a spacecraft with the goal of remaining the maximum possible time near the three bodies of the system, without the need of space maneuvers. This model is called "Precessing Inclined Bi-Elliptical Problem with Radiation Pressure" (PIBEPRP). The use of this model allow us to find important natural orbits for the exploration of one, two or even the three bodies of the system. These trajectories can be used individually or combined in two or more parts using orbital maneuvers.
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... Another interesting example is related to the study of stability around the triple asteroid system 2001SN263. Since this is the target of a proposed Brazilian space mission (Sukhanov et al. 2010; Macau et al. 2010), studies were made in order to identify the stable regions. In the first study (Araújo et al. 2012), prograde trajectories were considered, whose main purpose was to know the regions where leftovers (debris) from the origin of the triple system may still reside. ...
Astronautics & Astronomy - a Profitable Partnership
Article
Full-text available
  • Jul 2015
The connection between Astronautics and Astronomy is naturally straight forward. Astronomy is one of the oldest scientific areas along the human development, thousands of years. On the other side, Astronautics is much younger (a few centuries), but it actually started in the dreams and in the poetic literature well before we have had technology to accomplish a remarkable fact as the launching of the first artificial satellite in orbit of the Earth.
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... Inserted in this sector of contemporary space exploration, the mission ASTER was planned in cooperation with Russia to be the first Brazilian deep space mission. This mission intends to investigate the triple asteroid 2001-SN263 and has its launch date previously planned for 2017 [4, 5]. Among the instruments that will take part in this mission, the laser altimeter, named ALR (ASTER Laser Rangefinder), is being designed to meet the mission objectives concerning the investigation of the shapes, surfaces topographies and masses of the asteroids, together with the calculation of their masses, in addition to supporting the proximity navigation. ...
ALR - Laser altimeter for the ASTER deep space mission. Simulated operation above a surface with crater
Article
Full-text available
  • Oct 2015
To assist in the investigation of the triple asteroid system 2001-SN263, the deep space mission ASTER will carry onboard a laser altimeter. The instrument was named ALR and its development is now in progress. In order to help in the instrument design, with a view to the creation of software to control the instrument, a package of computer programs was produced to simulate the operation of a pulsed laser altimeter with operating principle based on the measurement of the time of flight of the travelling pulse. This software Simulator was called ALR_Sim, and the results obtained with its use represent what should be expected as return signal when laser pulses are fired toward a target, reflect on it and return to be detected by the instrument. The program was successfully tested with regard to some of the most common situations expected. It constitutes now the main workbench dedicated to the creation and testing of control software to embark in the ALR. In addition, the Simulator constitutes also an important tool to assist the creation of software to be used on Earth, in the processing and analysis of the data received from the instrument. This work presents the results obtained in the special case which involves the modeling of a surface with crater, along with the simulation of the instrument operation above this type of terrain. This study points out that the comparison of the wave form obtained as return signal after reflection of the laser pulse on the surface of the crater with the expected return signal in the case of a flat and homogeneous surface is a useful method that can be applied for terrain details extraction.
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... ASTER, the first deep space Brazilian mission, targets the group of asteroids in the system know as 2001 SN263, which is composed by a central body named Alpha and two satellites, the largest one orbiting further from the system's center is named Beta, while the smaller asteroid orbiting closer to Alpha is named Gamma. The objective of this mission is to explore the system, taking measurements and pictures from all three asteroids and, if possible, finalize the mission by touching down Alpha, [3, 7]. One of the many elements for the success of the mission is the ability of correct pointing and stabilization of the spacecraft, which is useful for the orientation of instruments and also for the navigation, which is based on a fixed ion-thruster technology; therefore, in order to change the trajectory for translation within the system, the attitude of the spacecraft needs to be changed. ...
Sliding mode attitude control using thrusters and pulse modulation for the ASTER mission
Article
Full-text available
  • Jan 2014
ASTER, the first Brazilian mission to the deep space, targets the exploration of the triple asteroid system known as 2001 SN263. The mission requires an attitude controller robust and capable of coping with the non-linearities and the uncertainties present during the exploration phase. For such requirements, this paper studies the applicability of two controllers, designed based on the sliding mode control (SMC) technique, one of the controllers include an adaptive law used to compensate for the spacecraft’s inertia variation. One application is performed where gain scheduling is used for controlling two different phases: exit from tumbling and track a dynamic reference. The actuators of the attitude control loops are impulsive thrusters. They are activated by pulse width modulation (PWM) or pulse width pulse frequency modulation (PWPFM). Simulation studies, performed in realistic scenarios, show that the SMC can maintain stability and performance when these modulation techniques are used to approximate the continuous commands. It is also shown that PWM can provide better performance, but at a higher control cost. In this sense, PWPFM is more appropriate with respect to the fuel consumption and activation times.
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Article
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We search for stable orbits in the vicinity of the triple asteroid system, 2001-SN263, which will be target of the deep space mission ASTER, currently under study by the Brazilian space agency (AEB). Our numerical simulations include gravitational forces caused by the three bodies of 2001-SN263, higher-order terms of the primary’s gravity field, planetary perturbations and solar radiation pressure. Due to the low gravity of the triple system, the spacecraft’s motion becomes complex and the faint gravity forces of the secondaries are exceeded by radiation pressure from the Sun. However, we show that the so-called ”terminator orbits” within the asteroid system at distances between 6-10 km to the primary body can be found. A spacecraft parked in such orbit will stay within the system for several months without the need to adjust its trajectory. Additionally, these stable orbits will allow investigating the entire primary body including its poles as well as the two secondary bodies. We also show that a laser altimeter, which is part of ASTER’s primary payload, will benefit significantly from these terminator orbits.
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(47171) 1999 TC36, A Transneptunian Triple
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