Lunar Lander (spacecraft): Difference between revisions
Content deleted Content added
unspeedy - more than one author involved |
←Blanked the page |
||
| Line 1: | Line 1: | ||
{{Infobox spacecraft |
|||
| name = Lunar Lander |
|||
| image = [[File:LLMoon.jpg|thumb|[[Lunar Lander]] depiction on [[Moon]] surface]] |
|||
| caption = |
|||
| mission_identifier = |
|||
| organisation = [[ESA]] |
|||
| major_contractors = [[Astrium]] |
|||
| bus = |
|||
| mission_type = Technology demonstrator, Exploration |
|||
| launch_date = 2018<ref name="derosa">{{cite journal|last=De Rosa|first=D.|coauthors=et al.|title=ESA Lunar Lander Mission|journal=8th International ESA Conference on Guidance, Navigation & Control Systems|date=5-10. June 2011|year=2011}}</ref> |
|||
| launch_vehicle = [[Soyuz-2_(rocket)#Soyuz_2.1b|Soyuz 2.1b]]<ref name="fisackerly">{{cite journal|last=Fisackerly|first=R.|coauthors=et al.|title=The ESA Lunar Lander Mission|journal=[[AIAA]]|year=2010}}</ref>| carrier_rocket = <!-- or American "launch_vehicle" can be used --> |
|||
| flight_number = |
|||
| launch_site = [[Guiana_Space_Centre#ELS_.2F_Soyuz_at_CSG|Guiana Space Centre - ELS]] |
|||
| mission_duration = Transfer: 2-4 months </br> Surface operations: ≈ 12 months |
|||
| mission_highlight = Autonomous soft precision landing employing hazard avoidance |
|||
| decay = |
|||
| return = <!-- for spacecraft designed to return to Earth --> |
|||
| return_site = <!-- for spacecraft designed to return to Earth --> |
|||
| nolink = <!-- set to anything to prevent linking COSPAR to NSSDC database --> |
|||
| COSPAR_ID = <!-- designations for pre-1963 launches should include a Greek letter, launches that failed to reach any orbit should not have a COSPAR --> |
|||
| webpage = |
|||
| mass = wet: 2200kg <br> dry: 780kg |
|||
| dimensions = height: 3.44m <br> diameter: 5.6m |
|||
| power = [[Solar panels]] |
|||
| batteries = |
|||
<!-- Orbit data --> |
|||
| orbit_reference = <!-- reference system --> |
|||
| orbit_regime = |
|||
| semimajor_axis = |
|||
| eccentricity = |
|||
| orbit_inclination = |
|||
| orbit_altitude = |
|||
| apoapsis = |
|||
| periapsis = |
|||
| orbital_period = |
|||
| longitude = |
|||
| repeat_interval = |
|||
| orbits_daily = |
|||
| repetitivity = |
|||
| orbit_swath = |
|||
| orbit_crossing = <!-- equator crossing --> |
|||
<!-- Interplanetary missions --> |
|||
| flyby_of = |
|||
| flyby_date = |
|||
| current_destination = |
|||
| satellite_of = |
|||
| orbital_insertion_date = |
|||
| orbits = |
|||
<!-- Planetary/Lunar landing --> |
|||
| Planet = [[Moon]] |
|||
| Planet_Landing = 2018 |
|||
| Planet_Coords = [[Lunar south pole]] |
|||
| Planet_Depart = |
|||
| LunarLandingDate = |
|||
| LunarLandingCoords = |
|||
| LunarLiftoffDate = |
|||
<!-- Instruments --> |
|||
| Instruments = |
|||
| Main_Instruments = |
|||
| Resolution = |
|||
| Spectral_Band = |
|||
| Data_Rate = |
|||
| SSR = <!-- solid-state recorder --> |
|||
| IMG_Resolution = |
|||
<!-- Transponders --> |
|||
| Transponders = |
|||
| Transponder_Capacity = |
|||
| Coverage = |
|||
| Twta output power = |
|||
| Bandwidth = |
|||
| EIRP = |
|||
| refs = |
|||
| below = |
|||
}} |
|||
The '''Lunar Lander''' (formerly known as [[MoonNext]]) is a robotic mission which sends a [[Lander (spacecraft)|lander vehicle]] to the [[Moon]]. The primary objective of the Lunar Lander mission is to demonstrate Europe’s ability to deliver payload safely and accurately to the Moon’s surface. More specifically the mission shall demonstrate the technologies required to achieve a soft precise landing while avoiding the various hazards (such as boulders or craters) which are present on the lunar surface. Central to achieving this objective is the Guidance, Navigation and Control (GNC) subsystem and its interfacing with other subsystems, primarily propulsion. The highly variable terrain of the South Pole region makes soft precision landing with hazard avoidance a must for the mission.<ref name="pradier">{{cite journal|last=Pradier|first=A.|coauthors=et al.|title=The First European Lunar Lander And The ESA-DLR Approach To Its Development|journal=61st International Astronautical Congress|date=27.-1.10.2010}}</ref> This technology will be an asset for future human exploration missions. The mission is led by [[European Space Agency|ESA's]] Human Spaceflight and Operations directorate and prioritizes usage of European technology. The [[lunar south pole]] has been selected as landing site for two reasons: |
|||
* Previous missions detected water ice in this area. On-board scientific payloads exploit this situation and conduct a variety of experiments. |
|||
* Continuous illumination by the [[Sun]] is given for several months. |
|||
Since the [[Moon]] lacks an atmosphere, all maneuvers are conducted propulsively. |
|||
== Mission Scenario == |
|||
=== Launch and Transfer === |
|||
Launching from Centre Spatial Guyanais, Kourou in late 2018 on a Soyuz launcher, the lander spacecraft is injected into its transfer orbit to the Moon by a Fregat-MT upper stage. Following an overall transfer of several weeks, via intermediate [[Highly elliptical orbit|highly elliptical orbit (HEO)]], the Lander injects itself into a low polar orbit around the Moon at 100 km altitude.<ref>{{cite web|last=Fisackerly|first=R.|title=The European Lunar Lander: Robotics Operations in a Harsh Environment|url=http://robotics.estec.esa.int/ASTRA/Astra2011/Presentations/Session%203A/01_fisackerly.pdf|publisher=ESA|accessdate=10 April 2012}}</ref> |
|||
=== Low Lunar Orbit === |
|||
The stay time in low lunar orbit (LLO) before landing depends on several factors including the need for checkout and calibration of the systems critical for landing, as well as the possible need for waiting time to ensure the correct orbit and Earth- Sun-Moon constellation and to accommodate margins for contingencies; this stay in orbit is expected to last from a number of weeks up to a maximum of 3 months. |
|||
=== Landing === |
|||
The lander performs a de-orbit burn close to the lunar north pole which decreases the orbit's perigee to about 15 km above the lunar south pole half an orbit later. During the de-orbit coasting period, visual feature matching with respect to the lunar surface is used to determine the lander's precise location and to ensure correct positioning at the beginning of final descend. Arriving at the south pole, the lander enters the final powered descend phase. Using its maximum thrust of about 3600N, the lander decelerates and descends propulsively . During this phase, the five main engines are successively shut down in a 5 - 3 - 1 sequence as the lander approaches its landing site and less thrust is required. Finer thrust levels are achieved using the ATV engines in off-modulation. At an altitude of about 2 km, the hazard detection and avoidance system (HDA) is able to see the primary landing site and to evaluate it. If the primary site is deemed unsafe, the HDA has the opportunity to command re-targetings to secondary landing sites . When a safe landing site is found, the lander performs vertical soft precision touch down at the selected landing site. |
|||
=== Surface Operations === |
|||
Once landed on the surface, the lander carries out critical operations such as deployment of its antenna and camera mast, |
|||
and relays the complete package of data relating to the descend and landing sequence back to Earth. The lander relies on direct line of sight communication with [[Earth]] as no relay satellite is planned for the mission. This configuration implies periods where no communication with Earth is possible because of Earth moving outside the lander's field of view. Similarly to the [[Sun]], [[Earth]] will be below the horizon following a monthly cycle due to Moon's tilted axis of rotation with respect its orbital plane. </br> |
|||
Nominal surface operations are then initiated which includes the deployment of specific payloads onto the lunar surface via robotic |
|||
arm, the activation of other static monitoring payloads on-board the lander, and ultimately the acquisition of surface |
|||
samples using the robotic arm for analysis by instruments on the lander. |
|||
== Landing Site == |
|||
The [[Lunar south pole|south polar region]] of the Moon has been identified as an important destination for future exploration missions due to the unique surface conditions found at certain sites in terms of solar illumination, the proximity of scientifically interesting locations such as permanently shadowed craters and the potential existence of resources which might be utilized. These factors combine to make this region a strong candidate for future human exploration and potentially even a long-term presence in the form of a lunar base. Recent orbital missions have provided strong evidence suggesting the south polar region’s potential as an important exploration destination. |
|||
</br> |
|||
The extended periods of continuous [[Sun]] illumination are unique to Moon's polar regions and allow the lander to be operated primarily by solar cells. However, favorably illuminated locations are expected to be close to hazardous areas such as steep slopes, bouldered terrains or shadowed territory. This setup requires the employment of dedicated autonomous, safe and precise landing technology. |
|||
== System == |
|||
=== Configuration === |
|||
[[File:LLConfiguration.jpg|thumb|middle|Lunar Lander vehicle dimensions.]] |
|||
The main body is tube shaped with four landing legs extending from the sides. |
|||
The circumference of the main body is covered with solar cells. The bottom side is dominated by the nozzles of the main thrusters while the top offers space for sensors and payload. |
|||
</br> |
|||
The lander will employ a robotic arm to retrieve soil samples for on-board analysis. |
|||
=== Precision Landing & Hazard Detection and Avoidance === |
|||
An exposed landing site on top of a crater rim or mountain is likely surrounded by hazards such as steep slopes. To avoid landing in an unsafe area, an autonomous hazard detection and avoidance (HDA) system is employed. The system is composed of a [[LIDAR]] and cameras which characterize the landscape underneath the lander during final descend. If the area is deemed unsafe, the system orders a retargeting to a safe landing area. |
|||
Since potential landing sites, which offer long periods of continuous illumination, are small in area,<ref name="derosa" /> a landing precision requirement of ≈200m radius has been derived. Compared to previous robotic lander missions, this requirement increases achievable landing precision |
|||
by orders of magnitude as shown in this table: |
|||
{| class="wikitable" |
|||
|- |
|||
! Mission !! Predicted landing accuracy !! Achieved Landing Accuracy |
|||
|- |
|||
| [[Spirit_rover|Spirit]] || ≈ 55 x 3 km (ellipse diameters)|| 10.1 km<ref name="Knocke">{{cite journal|last=Knocke|first=Philip|coauthors=et al|title=Mars Exploration Rovers Landing Dispersion Analysis|journal=AIAA/AAS Astrodynamics Specialist Conference and Exhibit|date=16-19.8.2004|location=Rhode Island, Providence}}</ref> |
|||
|- |
|||
| [[Opportunity_rover|Opportunity]] || ≈ 57 x 4 km (ellipse diameters)|| 24.6 km<ref name="Knocke" /> |
|||
|- |
|||
| [[Phoenix_%28spacecraft%29|Phoenix]] || ≈ 38 x 20 km (ellipse diameters)|| 7 km<ref>{{cite journal|last=Bonfiglio|first=Eugene|coauthors=et al|title=Landing-Site Dispersion Analysis and Statistical Assessment for the Mars Phoenix Lander|journal=Journal of Spacecraft and Rockets|date=5.9.2011|volume=48|issue=5|pages=784-797}}</ref> |
|||
|- |
|||
| [[SMART-1]] || - || 37 km<ref>{{cite journal|last=Racca|first=Giuseppe|title=SMART-1 from Conception to Moon Impact|journal=Journal of Propulsion and Power|date=5.9.2009|volume=25|issue=5|pages=993-1001}}</ref> |
|||
|- |
|||
| [[Mars_Science_Laboratory|MSL]] || 20 x 25 km<ref>{{cite journal|last=Kipp|first=Devin|title=Terrain Safety Assessment in Support of the Mars Science Laboratory Mission|journal=IEEE|date=2012}}</ref> (ellipse diameters) || - |
|||
|- |
|||
| Lunar Lander || 400 m (circle diameter) || - |
|||
|} |
|||
=== Power === |
|||
Planetary exploration missions have often turned to Radio-Isotope devices, whether RHUs or RTGs, to support thermal control and power generation in what are often extreme temperature and energy poor environments. However for Europe, where these technologies are currently unavailable, employing such devices have important technical and programmatic impacts. While activities investigating the development of RHUs and ultimately RTGs are proceeding within Europe, it is not expected that European devices would be available in the 2018 timeframe of the Lunar Lander mission.<ref name="pradier" /> </br> |
|||
Instead, the Lunar Lander is powered by solar arrays which are wrapped around the body tube. Once landed, the vehicles axis of symmetry will be almost perpendicular to the direction of the [[Sun]] ensuring continuously good illumination of the solar cells as the lander rotates with respect to the Sun (due to the rotation of the Moon). </br> |
|||
Batteries are used to bridge short periods without solar power. Solar power is unavailable in LLO when the lander goes into lunar [[eclipse]] and on the ground, when mountain peaks at the horizon cover the Sun. Landing operations will also be conducted relying solely on battery power. |
|||
=== Propulsion === |
|||
The spacecraft employs three types of engines: |
|||
# For attitude control, the lander uses sixteen 22N thrusters. |
|||
# Six 220N [[Automated Transfer Vehicle|ATV]] thrusters<ref>{{cite web|title=200 N Bipropellant Thrusters for ESA's ATV|url=http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropellant-thrusters/220n-atv-thrusters.html|publisher=[[Astrium]]|accessdate=5 April 2012}}</ref> complement the attitude control system and provide additional hovering thrust. This task demands varying thrust levels from the engine which is accomplished through pulsed operation<ref>{{cite web|title=Lunar lander firing up for touchdown|url=http://www.esa.int/export/esaCP/SEMSEF7YBZG_Expanding_0.html|publisher=ESA|accessdate=10 April 2012}}</ref> as the engine itself is non-throttable. |
|||
# Flight maneuvers such as apogee raise burns are accomplished using one of five 500N European Apogee Motors.<ref>{{cite web|title=500 N Bipropellant European Apogee Motor (EAM)|url=http://cs.astrium.eads.net/sp/spacecraft-propulsion/apogee-motors/500n-apogee-motor.html|publisher=[[Astrium]]|accessdate=5 April 2012}}</ref> All five engines will be needed to deliver sufficient thrust to deccelerate the lander from low lunar orbital velocity for controlled final descend. |
|||
[[File:LLSpace.jpg|thumb|[[Lunar Lander]] depiction in low lunar orbit with thrusters firing]] |
|||
=== Navigation === |
|||
The vehicle uses traditional means of navigation during its transfer trajectory to the moon. This includes employment of an [[Inertial measurement unit|IMU]] ([[accelerometer]] and [[gyroscope]]), [[Star_tracker#Star_tracker|star trackers]] and [[Sun_sensor#Sun_sensor|sun sensors]]. Furthermore, [[Time of flight|range]] and [[Doppler effect|Doppler]] measurements from Earth will help to determine the spacecraft's position and velocity, respectively. |
|||
</br> |
|||
In LLO and during descend, other means of navigation need to be considered. Early study phases identified the need to use high altitude vision-based absolute navigation, along with relative visual navigation.<ref name="derosa"/> These advanced techniques allow an improvement of the navigation performances, as compared to traditional techniques, such as inertial navigation and Earth-ground-based orbit determination. Furthermore, in order to guarantee soft landing and to reach the start of the approach phase within a tight corridor, an on-board long-range altitude measurement is required which will be available through visual navigation. |
|||
</br> |
|||
Additionally, a laser altimeter will aid precise position determination, during final descend. |
|||
</br> |
|||
== Science == |
|||
A selection of possible Lunar Lander science payloads has been established according to objectives aligned with human exploration preparation. This includes detailed investigation of surface parameters of strong significance for future operations on the surface, be they human and/or robotic. </br> |
|||
Specific payload packages have been defined to address the: |
|||
* microscopic properties of dust, including shape & size distribution, and its composition |
|||
* plasma and electric field environment on the lunar surface, and the behaviour of dust within that environment |
|||
* feasibility of making radio astronomy measurements from the lunar surface |
|||
* potential volatile content of regolith (e.g. OH) |
|||
* effects of radiation on biology at the lunar surface |
|||
* camera package for visual data from the south pole environment |
|||
All of these payloads are either statically accommodated on the lander body, held at distance from the lander by dedicated booms, or are deployed in close proximity to the lander (1-2m) by robotic arm. Payloads which analyze samples of regolith close-up will receive small amounts of material gathered from the vicinity of the lander by an acquisition device on the end of the robotic arm. Final payload selection has yet to be conducted.<ref name="fisackerly" /> |
|||
== Current Project Status == |
|||
In 2010, three feasibility studies have been conducted in parallel by [[Astrium|EADS Astrium]], [[OHB]] and [[Thales Alenia Space]]. In August 2010, Astrium has been selected as prime contractor for further system definition studies which will culminate in a mid 2012 preliminary system requirements review. It is expected that additional funding will be allocated to the project at the November 2012 European Ministerial Conference which discusses the eighth European [[Framework programme|Framework Programme for Research and Technological Development]]. |
|||
== References == |
|||
{{reflist}} |
|||
<!--- After listing your sources please cite them using inline citations and place them after the information they cite. Please see http://wiki.riteme.site/wiki/Wikipedia:REFB for instructions on how to add citations. ---> |
|||
* |
|||
* |
|||
* |
|||
* |
|||
{{Moon spacecraft}} |
|||
[[Category:Missions to the Moon]] |
|||
[[Category:European Space Agency]] |
|||
[[Category:2018 in spaceflight]] |
|||