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CHRIS/PROBA Workshop 28/04/2004
Orbital parameters:• Altitude: 681 - 561 km• Near polar (inclination of 97.9°)• Sun-synchronous • Period 96.97min
PROBA 1 has been launched on 21 October 2001
PROBA 1 launchPROBA 1 launch
CHRIS/PROBA Workshop 28/04/2004
start date stop date Activity
22 October 2001 Launch
22 October 2001 24 October 2001 LEOP
24 October 2001 April 2002 Commissioning
April 2002 April 2003 Technology Demonstration mission
April 2002 Start of CHRIS instrument calibration campaign & science mission
Continuous Implementation and in-flight testing of improvements of the system and operations
October 2002 Priority given to science mission
Jan 2003 March 2003 Intensive campaign to further improve system stability and reliability in preparation of ScientificUtilisation Mission
April 2003 now Scientific Utilisation Mission, main mission priority
June 2003 Start of utilisation of Kiruna as additional downlink station
PROBA 1 early activitiesPROBA 1 early activities
CHRIS/PROBA Workshop 28/04/2004
ESA technology demonstration program (GSTP)(1) In orbit demonstration of spacecraft technology(2) Payload complement
– CHRIS: Compact High Resolution Imaging Spectrometer– HRC: High Resolution Telescope– SREM, DEBIE, MRM: Earth environment monitors
Operations centre located at ESA-Redu ground station (B)
PROBA 1 Data (1)PROBA 1 Data (1)
CHRIS/PROBA Workshop 28/04/2004
• Mass : 94 kg• Volume : 80cm x 60cm x 60cm• Power : 40 to 120 W• High accuracy and agile ACNS
PROBA 1 Data (2)PROBA 1 Data (2)
CHRIS/PROBA Workshop 28/04/2004
Mission managementMission management
Main elements (related to CHRIS):
•PROBA 1 Steering Group (ESA) in charge of overall mission management•CHRIS Steering Group (BNSC) in charge of CHRIS utilisation•Campaign Unit (ESA) in charge of the definition and the organisation of the CHRIS Observation Plan•RSAC (UK) in charge of CHRIS day to day planning•SIRA (UK) in charge of level 0 processing and data distribution•ESA Redu (B) in charge of spacecraft operations•Industry in charge of technical project support
CHRIS/PROBA Workshop 28/04/2004
PROBA 1 statusPROBA 1 status
•Spacecraft is operating on its nominal chain•Degradation of power subsystem (solar arrays and battery) is compatible with the current mission and further extension is possible with some saving measures (limitation in summer of earth environment instruments)•Degradation of radiation sensitive items (electronics, CCD) was observed but remains compatible with the mission and a possible extension•Orbital natural decay and drift from SSO are very low (< 10 km semi-major axis)•Ground segment status (addressed later)Drift of the orbital plane wrt the sun (i.e. drift from sun-synchronicity): <2°/year (< 8min) in the direction of noon.
apogee height
70387040704270447046704870507052705470567058
14-Sep-01
14-Jan-02 16-May-02
15-Sep-02
15-Jan-03 17-May-03
16-Sep-03
date
km
perigee height
6922
6924
6926
6928
6930
6932
14-Sep-01
14-Jan-02 16-May-02
15-Sep-02
15-Jan-03 17-May-03
16-Sep-03
date
km
CHRIS/PROBA Workshop 28/04/2004
PROBA 1 EO related performancesPROBA 1 EO related performances
•Spacecraft pointing performances are in line with expectations,•Data link is nominal (some data loss on board),•Thermal stability of CHRIS is adequate
The main remaining issue is related to the spacecraft robustness which is acceptable but still includes anomalies causing losses of images (success rate addressed later) .
CHRIS/PROBA Workshop 28/04/2004
Platform stability, including onboard computer rebootsThe main problems still encountered on board after the end of the commissioning phase were the relatively frequent software reboots
and the instable attitude control. Cold reboots resulting in the loss of not yet dumped image data and reconfiguration of the spacecraft into safe mode occurred typically once every 3-6 days or once every few weeks. Although the frequency of such events varied during the mission these events were found to be related and all had a potential impact on the spacecraft scientific return (less to the technology demonstration return). Depending on the case by case situation, this impact could consist in:
•the loss of planned imaging activities between two ground segment passes•the loss of imaging data •quality loss of imaging data
Considerable effort has been put into the investigations of these events and into the definition and implementation of containment and corrective actions. As a result most of the mechanisms leading to these events were identified and corrected or worked-around, resulting finally in a complete resolution and a stable platform in April 1st 2003.
Infant anomaliesInfant anomalies
Centre timesThe CHRIS image times that the PPU manager takes from the ACNS represent centre times of the image. No factor was used to start the imaging sooner. Consequently, the selected target was not in the centre of the image, but always at the edge of the image (the image scan starts at the target). Therefore, the 5 images taken with CHRIS were not of the exact same area. Forward scans would show an area starting with the target and moving in the flight direction. Backward scans would also start at the target and move in the opposite of the flight direction. A patch in RAM has been uploaded with a configurable time offset, that will correct the values obtained from the ACNS. This patch successfully adjusts the start time of the CHRIS imaging, such that the target is located in the centre of the image. Depending on the image taken (e.g. number of lines), the time offset needed can be up to 5 seconds for a 10 second image.Furthermore, the presence of this patch provides the spacecraft operators to choose between overlapping images (images of the same area taken under different angles) or to “pave” the images in order to increase the actual field of view.
CHRIS/PROBA Workshop 28/04/2004
Thermal Subsystem (CHRIS)Thermal Subsystem (CHRIS)
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
0.0 24.0 48.0 72.0
hours in terrestrial
CH
RIS
tem
pera
ture
(°C
)
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0.0 20.0 40.0 60.0 80.0 100.0
orbit time (minutes)
tem
pera
ture
(°C
)
COLD_MODEL_CHRISHOT_MODEL_CHRISMEASURED_CHRIS
In orbit results: CHRIS TemperatureTransient from Bdot to Terrestrial
Measurements versus simulation results
CHRIS/PROBA Workshop 28/04/2004
InstrumentsInstruments
CHRIS/PROBA Workshop 28/04/2004
High Resolution Camera (HRC)• Panchromatic • 3D Packaging Technology CCD• Fixed target pointing• Strong requirements platform stability• 8 m ground resolution• Image size 4 x 4 km
High Resolution CameraHigh Resolution Camera
CHRIS/PROBA Workshop 28/04/2004
Terrestrial : Fixed target pointingTerrestrial : Fixed target pointing
4 km
Line-of-sightof imager
HRCImage
No scanning: ground speed = 0 m/sec
Fixed target pointing• Used for HRC and WAC imaging and optimal ground contact
• HRC: 8 m resolution
• Off-track pointing of 25° possible
CHRIS/PROBA Workshop 28/04/2004
High Resolution Camera resultsHigh Resolution Camera results
CHRIS/PROBA Workshop 28/04/2004
CHRISCHRIS
• Bi-directional Reflectance Distribution Function measurements
• 19 spectral bands (415 - 1050 nm)• Push-broom• 20 m resolution• Image size 15 x 15 km
Compact High Resolution Imaging Spectrometer (CHRIS)
CHRIS/PROBA Workshop 28/04/2004
Terrestrial : ImagingTerrestrial : Imaging
15km
Beginimaging
Endimaging
Line-of-sightof imager
Image2Image4Image5 Image1Image3
Scanning speed = 1/5 of spacecraft ground speed
Imaging mode:• CHRIS BRDF images
• 5 images per sequence in observation cone with 55° co-elevation angle
• Motion compensation of factor 5 wrt traditional push-broom! images takes 10 seconds
• 20 m resolution
• Off-track pointing of 25° possible
CHRIS/PROBA Workshop 28/04/2004
Earth targettingEarth targetting
• Prediction of the satellite flying by a target over the next day within some Roll constraints.• Fine prediction and count down for fixed target pointing and CHRIS imaging.• Used for sorting/selecting multiple targets and implement command sequence relative to fly-by (e.g
switch on camera 100 sec before image taking).
γ*
γSpacecraftUser-selected
imaging targetPitch
Earth
γmax
Observation Cone
rREL
rrT
αOBS0)(sin)()(cos)(0cos =+⇒= tutBtutA
dtd γ
TREL
TREL
TREL
TREL
rrrr
rrrr rr
rr
rr ⋅−=⋅−=γcos
Target prediction
Find the extrema of cosγ
CHRIS/PROBA Workshop 28/04/2004
ConclusionConclusion
The PROBA mission - although designed as a technology demonstrator with a lifetime of 1 year – has demonstrated adequate capabilities for science, disaster monitoring, education and outreach by the Earth observation community. The life time can be further extended for a period of at least 2 years (this extension is based on the status of the limited life on board items not on reliability estimation).
The extension would require adequate support to cover technical support from project at ESTEC and industry in addition to the operation of the ground segment elements at Redu, Sira, RSAC, ESRIN.
Depending on the mode of operations PROBA can support EO needs with a capability ranging from 2 sets of 5 multi-spectral, multi-angle scientific images to 50 push-broom 3 bands pseudo-colour images per day (depending on viewing opportunities and ground station visibility). Additional capability would require modification of the ground station locations.
