Changes between Initial Version and Version 2 of TBR/UserApp/Space/ProbaV


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Timestamp:
Dec 4, 2011, 1:23:13 PM (8 years ago)
Author:
Iliyankatsarski
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/* ProbaV */ new section

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  • TBR/UserApp/Space/ProbaV

    v1 v2  
     1= ProbaV =
     2
     3
     4#REDIRECT [wiki:ESA_Proba-V ESA Proba-V]
     5=  ProbaV  =
     6
     7
     8
     9[[TOC(TBR/UserApp/Space/ProbaV, depth=2)]]
     10
     11The ‘V’ in its name stands for Vegetation: Proba-V will fly a reduced-mass version of the Vegetation instrument currently on board the Spot satellites to provide a daily overview of global vegetation growth.
     12
     13{| align="center"
     14|+'''PROBA V'''
     15|-
     16|[wiki:File:Probav-shiny_large0.jpg 450px]
     17|}
     18
     19 
     20Bearing a different designation from its predecessors, Proba-V is an operational as well as experimental mission, designed to serve an existing user community.
     21
     22The aim is to guarantee data continuity for the Vegetation dataset once the current Spot missions end.
     23
     24{| border="1"
     25|+ '''Proba-V facts and figures'''
     26|-
     27|Launch date:
     28|mid-2012
     29|-
     30|Mass:
     31|160 kg
     32|-
     33|Orbit:
     34|Sun-synchronised polar orbit, 820 km, with a 10:30 AM local time at the descending node
     35|-
     36|Instrument:
     37|Newly designed version of the Vegetation instrument flown on the Spot series
     38|-
     39|Guest technology payloads:
     40|Gallium Nitride amplifier incorporated in communication subsystem; Energetic Particle Telescope and one other payload to be decided at a later stage
     41|-
     42|Prime contractor:
     43|Qinetiq Space Belgium
     44|-
     45|Payload developer:
     46|OIP Space Systems
     47|-
     48|Ground Station:
     49|Satellite’s mission control centre in Redu, Belgium complemented by a data reception station to be located in the north of Europe.
     50|-
     51|Launcher:
     52|To be decided – designed to be compatible with Vega, Soyuz or Falcon 1E launchers.
     53|}
     54
     55=  PROBA-V (Project for On-Board Autonomy - Vegetation) =
     56
     57
     58The PROBA-V (Vegetation) mission definition is an attempt, spearheaded by ESA and CNES, to accommodate an improved smaller version of the large VGT (Vegetation) optical instrument of SPOT-4 and SPOT-5 mission heritage on a small satellite bus, such as the one of PROBA-2.
     59
     60As of 2008, small satellite technologies have reached a level of maturity and reliability to be used as a platform for an operational Earth observation mission. Furthermore, advancements in the techniques of detectors, optics fabrication and metrology are considered sufficiently mature to permit the design of a compact multispectral optical instrument. 1) 2) 3) 4) 5) 6) 7) 8) 9) 10)
     61
     62The C/D Phase started in July 2010. The system CDR (Critical Design Review) took place in the spring of 2011. The acceptance review is planned for Dec. 2011 and the flight acceptance review is planned for the spring of 2012.. ESA is responsible for the overall mission, the technological payloads and for the launcher selection.
     63
     64Background: The VGT instruments (VGT1 & VGT2), each with a mass of ~160 kg and fairly large size, have provided the user community with almost daily global observations of continental surfaces at a resolution of 1.15 km on a swath of ~2200 km. The instruments VGT1 on SPOT-4 (launch March 24, 1998) and VGT2 on SPOT-5 (launch May 4, 2002) are quasi similar optical instruments operating in the VNIR (3 bands) and SWIR (1 band) range.
     65
     66The Vegetation instruments were jointly developed and funded by France, Belgium, Italy, Sweden, and the EC (European Commission). The consortium of CNES, BelSPO (Federal Public Planning Service Science Policy), SNSB (Swedish National Space Board) and VITO (Flemish Institute for Technological Research) is providing the user segment services (data processing, archiving, distribution). Vegetation principally addresses key observations in the following application domains:
     67
     68 *  General land use in relation to vegetation cover and its changes
     69
     70 *  Vegetation behavior to strong meteorological events (severe droughts) and climate changes (long-term behavior of the vegetation cover)
     71
     72 *  Disaster management (detection of fires and surface water bodies)
     73
     74 *  Biophysical parameters for model input devoted to water budgets and primary productivity (agriculture, ecosystem vulnerability, etc.).
     75
     76As of 2008, a Vegetation archive of 10 years of consistent global data sets has been established permitting researchers access on a long-term basis. The SPOT-5 operational lifetime is estimated to expire in 2012. Pleiades, the next French satellite for Earth Observation, is solely dedicated to high-resolution imaging (on a fairly narrow swath) and will not embark any instrument providing vegetation data.
     77
     78Since the SPOT series spacecraft will not be continued and the SPOT-5 spacecraft will eventually fail — there is of course a great interest in the EO user community to the Vegetation observation in the context of a smaller mission, affordable to all concerned. 11)
     79
     80PROBA-V will continue the production of Vegetation products exploiting advanced small satellite technology. However, this implies in particular a redesign of the Vegetation payload into a much smaller unit to be able to accommodate it onto the PROBA bus.
     81
     82Overview of key requirements of the PROBA-V mission - and some improvements compared to SPOT/Vegetation:
     83
     84 *  Data and service continuity: filling the gap between SPOT-VGT and the Sentinel-3 mission
     85
     86 *  Spectral and radiometric performance identical to VGT
     87
     88 *  GSD: 1 km mandatory, improved GSD is highly disirable: 300 m (VNIR bands), 600 m (SWIR band). Image quality and geometric accuracy, equal to or better than SPOT-VGT
     89
     90 *  Provision of daily global coverage of the land masses in the latitudes 35º and 75º North and in the latitudes between 35° and 56° South, with a 90% daily coverage of equatorial zones - and 100% two-daily imaging, during day time, of the land masses in the latitudes between 35º North and 35º South..
     91
     92
     93{| align="center"|[wiki:File:ProbaV_Auto12.jpeg File:ProbaV Auto12.jpeg]|}
     94
     95Figure 1: Artist's view of the PROBA-V spacecraft (image credit: ESA) 12) 13)
     96
     97An extensive feasibility study and trade-off work was undertaken to identify a solution that could meet not only the technical challenges, but that could also be developed and tested within a tight budget of a small satellite mission.
     98
     99The PROBA-V project of ESA includes the Space Segment (platform contract award to QinetiQ Space NV of Kruibeke, Belgium - formerly Verhaert), the Mission Control Center (Redu, Belgium) and the User Segment (data processing facility) at VITO NV. VITO (Vlaamse instelling voor technologisch onderzoek - Flemish Institute for Technological Research) is located in northern Belgium. VITO’s processing center of VGT1 and 2 data (SPOT-4 and SPOT-5) is operational since 1999. VITO is also the prime investigator and data service provider of PROBA-V for the user community including product quality control. 14)
     100
     101Implementation schedule:
     102
     103 *  The Phase B of the project started in January 2009
     104
     105 *  SRR (System Requirements Review) is in Q4 of 2009
     106
     107 *  PDR (Preliminary Design Review) in Q2 of 2010
     108
     109 *  HMA (Heterogeneous Mission Access) and QA4EO (Quality Assurance for Earth Observation) implementation for user data. Planned interoperability with GSCDA V2 (GMES Space Component Data Access Version 2).
     110
     111[wiki:File:ProbaV_Auto11.jpeg File:ProbaV Auto11.jpeg]
     112Figure 2: PROBA-V project organization (image credit: ESA, Ref. 9)
     113= Spacecraft: =
     114
     115
     116An industrial team, led by QinetiQ Space NV (Belgium), is supported by several European subcontractors and suppliers, and is responsible for the development of the flight satellite platform, the vegetation payload and the Ground Segment.
     117
     118The spacecraft bus (fully redundant) is of heritage from the PROBA-1 and PROBA-2 missions (structure, avionics, AOCS, OBS with minor modifications). The PROBA-V spacecraft has a total mass of ~160 kg, and a volume of 80 cm x 80 cm x 100 cm. The three-axis stabilized platform is designed for a mission lifetime of 2.5 years (Ref. 7). 15)
     119
     120The spacecraft resources management is built around ADPMS (Advanced Data and Power Management System), which is currently flying on PROBA-2. The data handling part of ADPMS is partitioned using compact PCI modules. A cold redundant mass memory module of 16 Gbit is foreseen for PROBA-V. The newly developed mass memory will use NAND flash technology.
     121
     122The power distribution and conditioning part of ADPMS supplies an unregulated bus, with each equipment having its internal DC/DC converter. The power conditioning system is designed around a Li-ion battery.
     123
     124[wiki:File:ProbaV_Auto10.jpeg File:ProbaV Auto10.jpeg]
     125Figure 3: PROBA-V spacecraft accommodation (image credit: QinetiQ Space)
     126
     127AOCS (Attitude and Orbit Control Subsystem) provides three-axis attitude control including high accuracy pointing and maneuvering in different spacecraft attitude modes. The AOCS SW is an extension of the one of PROBA-2, including the following algorithms required by the on-board autonomous mission and payload management: 16)
     128
     129- Prediction of land/sea transitions using a land sea mask to reduce the amount of data generated
     130
     131- Optimization of attitude in Sun Bathing mode to enhance incoming power while avoiding star tracker blinding
     132
     133- Momentum dumping without zero wheel speed crossings during imaging
     134
     135- Estimations of remaining spacecraft magnetic dipole to reduce pointing error
     136
     137- Autonomous avoidance of star tracker Earth/Sun blinding
     138
     139- Inertial mode with fixed scanning rate for moon calibration.
     140
     141The AOCS hardware selection for PROBA-V consists of a high accuracy double star tracker head, a set of reaction wheels, magnetotorquers, magnetometers and a GPS receiver.
     142
     143The main AOCS modes are: Safe, Geodetic, Sun Bathing and Inertial mode.
     144
     145- The satellite Safe mode is used to detumble the spacecraft after separation from the launcher and it will be used to recover from spacecraft anomalies.
     146
     147- The Geodetic mode is used during nominal observation of the Earth’s vegetation. In this mode the payload is pointed towards the geodetic normal to the Earth’s surface. An extra steering compensation, yaw-steering, is added in this mode, to minimize the image distortion caused by the rotation of the Earth. This yaw-steering maneuver ensures that the spectral imagers are oriented such that the lines of pixels are perpendicular to the ground-trace at each moment. In this mode the star trackers and the GPS receiver are used as sensors and the reaction wheels as actuators.
     148
     149- On each orbit, the spacecraft enters the Sun Bathing mode from -56º latitude until entry of eclipse. This is to enhance the incoming power.
     150
     151- The Inertial mode coupled with an inertial scanning of the Moon at a fixed rate is used for monthly radiometric full moon instrument calibration purposes. The pointing towards the moon takes 2.5 min, 9 min for scanning the moon and 2.5 min to return to nominal observation mode. It is sufficient to have the moon in the FOV of the SI (Spectral Imager) for a number of pixels.
     152
     153Beyond the technology demonstration through the PROBA program, it is also noted that the AOCS software technology developed in the course of this program is now the baseline of the AOCS of a major operational mission of the GMES (Global Monitoring for Environment and Security) program: Sentinel-3. NGC Aerospace Ltd (NGC) of Sherbrooke, (Québec), Canada was responsible for the design, implementation and validation of the autonomous GNC (Guidance, Navigation and Control) algorithms implemented as part of the AOCS software of PROBA-1 and PROBA-2. NGC has the same responsibilities for the PROBA-V mission (Ref. 16).
     154
     155EPS (Electric Power Subsystem): The PVA (Photo-Voltaic Array) uses GaAs triple junction cells with an of efficiency of 28%. To obtain the operating voltage of 31.5 V, 18 cells are included in each string in series with a blocking diode. The PVA consists of a total of 25 solar strings taken into account the loss of one string on the most contributing PVA panel. The average solar string power under EOL conditions (summer solstice and T = 40°C) yields 12.8 W. The maximal incoming power at EOL during an orbit is 144 W. The energy budget for PROBA-V is derived for a bus power consumption of 140 W assuming a worst case day in the summer and while not taken into account the effect of albedo. A worst case power budget analysis indicated a maximum capacity discharge of 1.66 Ah. Use of a Li-ion battery. The battery cells provide a capacity of 1.5 Ah per string. The PROBA-V battery is sized to 12 Ah taking into account capacity fading and loss of a string.
     156
     157Launch: A launch of the PROBA-V spacecraft as a secondary payload is planned for Q4 2012. The primary launcher is currently assumed to be Vega with the VESTA adapter.
     158
     159Orbit: Sun-synchronous orbit, altitude = 820 km, inclination = 98.8º, LTDN (Local Time on Descending Node) = 10:30 hours (with a drift limited between 10:30 and 11:30 AM during the mission lifetime).
     160
     161RF communications: S-band for TT&C transmissions and low-gain antennas with omni-directional up- and downlink capability. The uplink symbol rate will be fixed at 64 ks/s, while the downlink can be set to a high rate (< 2 Ms/s) for nominal imaging or to a low rate at 329 ks/s for off-nominal conditions. The CCSDS protocol is used for the TT&C transmissions.
     162
     163X-band downlink of payload data is in X-band at a data rate of 35 Mbit/s. The onboard mass memory is 88 Gbit. The Redu station (Belgium) is being used for TT&C communication services. The X-band uses two cold redundant high-rate X-band transmitters and two nadir pointing isoflux antennas, both RHCP.
     164
     165The S-band transceivers will be connected to RS422 outputs (cross strapped) of ADPMS while the X-band transmitters (8090 MHz) will be connected to the LVDS outputs not cross-strapped. The X-band link budget results in a link margin of 6 dB which will allow a reduction of the RF output power. Therefore the X-band transmitter will be designed (customer furnished item) to support various output power settings such that after commissioning, a lower output power might be selected.
     166
     167Data compression: The massive amount of data produced by the instrument is beyond the capabilities of the bandwidth available on board of a small satellite. Data are reduced by using a lossless data compression algorithm implemented in a specific electronics. The data compression ratio obtained using standard CCSDS compression algorithms (CCSDS 133.0 B-1) is shown in Table 2.
     168
     169Spectral band
     170       
     171
     172Compression ratio
     173
     174Blue 10.8
     175
     176Red 7.2
     177
     178NIR 5.4
     179
     180SWIR 2
     181
     182Table 2: Overview of compression rates
     183
     184The selection of an S-band transceiver and the development of an innovative and generic X-band transmitter for small satellites has been initiated in a collaborative program between CNES and ESA and is funded under GSTP-5 (General Support Technology Program-5). The X-band transmitter is a high-performance device optimized for the needs and constraints of small platforms for which small volume, low mass, low power consumption, and low cost cost are important parameters. Moreover, some key features such as modulation (filtered Offset-QSK), coding scheme (convolutional 7 ½), data and clock interfaces (LVDS packet wire serial interface) have been selected in compliance with CCSDS recommendations, but also to ease the interoperability with most of the existing on-board computers and ground station demodulators. 17)
     185
     186The development of the new X-band transmitter is based almost exclusively on COTS components to achieve at the same time high performances and low recurrent cost. The transmitter also features an innovative functionality with an on-board programmable RF output power from 1-10 W which allows to match finely with the chosen bit rate, and to reduce as much as possible the margins of the link budget and therefore the consumption power. PROBA-V is the first mission to use this newly developed transmitter. The transmitter has a mass of 1 kg, a size of 160 mm x 115 mm x 46 mm, an in-orbit life time of 5 years, and a radiation hardness of 10 krad. Data rates from 10-100 Mbit/s are available. The X-band transmitter was manufactured by TES Electonic Solutions of Bruz, France. 18)
     187
     188[wiki:File:ProbaV_AutoF.jpeg? File:ProbaV AutoF.jpeg?]
     189Figure 4: Overview of the transmitter architecture (CNES, TES)
     190
     191[[File:ProbaV_AutoE.jpeg]]
     192Figure 5: Photo of the X-band transmitter (image credit: CNES, ESA)