About ChelysAbout Chelys

About ChelysAbout Chelys

Software development and integration for the space sector since 1996Software development and integration for the space sector since 1996

Service provider for some of the most important space agencies (ESA, Eumetsat)Service provider for some of the most important space agencies (ESA, Eumetsat)

Multi-mission systems, quality control, image processing and cataloguing of satellite dataMulti-mission systems, quality control, image processing and cataloguing of satellite data

SRRSSRRS

Processing high resolution data requires a high resource usage

In the ground segment the processing of HR data is usually on-request

Only data at low resolution or a small part of those in high resolution are processed systematically

Processing high resolution data requires a high resource usage

In the ground segment the processing of HR data is usually on-request

Only data at low resolution or a small part of those in high resolution are processed systematically

We have developed an architecture,SRRS – Satellite Rapid Response Systemable to start from raw data (level0), that in general is available just a few seconds after being downloaded from the satellite.

We have developed an architecture,SRRS – Satellite Rapid Response Systemable to start from raw data (level0), that in general is available just a few seconds after being downloaded from the satellite.

SRRS ArchitectureSRRS Architecture

Distributed architecture with a central catalogue and a data driven processing systemDistributed architecture with a central catalogue and a data driven processing system

SRRSSRRS

I nternet Link

Acquisition

User Access

Front End Processor&

Level0 Generator

MIRAVIProcessing System

Data Driven InterfaceSRRS receives data through a FTP push or via SMB mount

SDS FacilityAs soon as the level0 were generated, they are sent to the local SRRS subsystem

Firewall

WEB (port 80)Contents are distributed by a HTTP server

FTP Server (port 21)Raw Data, User requests and Update Files are received through a local FTP server

Processing System Processing System Processing System

Central Database and Catalogue

SRRS Data FlowsSRRS Data Flows

Three main data flows: processing, consultation and on-request orderingThree main data flows: processing, consultation and on-request ordering

SRRSSRRS

Qualitiy Control andImage Processing

Level0 Ingestion

FTP or SMBUpdate File

FTP Put

Central Databaseand Catalogue

Local Archive ofQuality Control Data

and Images

Local Archive RAID Array

User

Content Distribution

HTTP

User Notification

SMTP

Temporary archive ofprocessed images

Local Archive RAID Array

UserCentral Database and Catalogue

User

User RequestSubmission

HTTP

RemoteProcessing System

User RequestFTP

Central Database and Catalogue

User

CatalogueQueryHTTP

End User

Reports andImages Reqests

HTTP

CatalogueReplyHTTP

RemoteProcessing System

User

Reports and Images

DownloadHTTP

Data Processing

Catalogue Consultation

On Request Processing

Raw DataProvider

ALOS/AVNIRALOS/AVNIR

WEB InterfaceWEB Interface

ALOS/AVNIRALOS/AVNIR

WEB InterfaceWEB Interface

ALOS/AVNIR2ALOS/AVNIR2

AVNIR2 represented a new challenge as we wanted to work on a sensor with a much higher resolution than MERIS.

AVNIR2 represented a new challenge as we wanted to work on a sensor with a much higher resolution than MERIS.

ALOS/AVNIR2ALOS/AVNIR2

Now we are going to present the results:Now we are going to present the results:

•Raw Data Image Processor (a new processing system that can be added to the existing SRRS infrastructure)

•Raw Data Image Processor (a new processing system that can be added to the existing SRRS infrastructure)

•Instrument Process Facility (IPF)•Instrument Process Facility (IPF)

Both systems start from the raw data relative to the AVNIR2 bands and from the Telemetry. The first system performs quality control and true color image generation, the other is a true IPF made to generate products.

Both systems start from the raw data relative to the AVNIR2 bands and from the Telemetry. The first system performs quality control and true color image generation, the other is a true IPF made to generate products.

Images Images

When we started to develop the image processor we found that the model used to generate MERIS images was not sophisticated enough to generate realistic images using an instrument with a resolution as high as AVNIR’s.

When we started to develop the image processor we found that the model used to generate MERIS images was not sophisticated enough to generate realistic images using an instrument with a resolution as high as AVNIR’s.

ALOS/AVNIR2ALOS/AVNIR2

AVNIR2 Image ProcessorAVNIR2 Image Processor

That’s why we have implemented the reflectance calculation with the atmospheric correction.

That’s why we have implemented the reflectance calculation with the atmospheric correction.

Images Images

These adjustments are important in producing accurate band ratio indexes. The system provides progressive, cumulative adjustments:

These adjustments are important in producing accurate band ratio indexes. The system provides progressive, cumulative adjustments:

ALOS/AVNIR2ALOS/AVNIR2

Calculation of ReflectanceCalculation of Reflectance

• First it applies sensor gain and offset values to convert raw image value to calibrated radiance

• First it applies sensor gain and offset values to convert raw image value to calibrated radiance

• Then it uses the solar elevation angle to compute the TOA reflectance• Then it uses the solar elevation angle to compute the TOA reflectance

• Next, it corrects the TOA values for the additive (band dependent) effects of atmospheric path reflectance (haze)

• Next, it corrects the TOA values for the additive (band dependent) effects of atmospheric path reflectance (haze)

• Then path reflectance values are computed empirically from band histograms• Then path reflectance values are computed empirically from band histograms

• Finally it corrects for (band dependent) atmospheric attenuation (absorption) effects to compute the scaled reflectance of the surface materials

• Finally it corrects for (band dependent) atmospheric attenuation (absorption) effects to compute the scaled reflectance of the surface materials

Images Images

Now we will show you the images prior to correction and how we were able to improve them.

Now we will show you the images prior to correction and how we were able to improve them.

ALOS/AVNIR2ALOS/AVNIR2

Raw Data ImageRaw Data ImageCalibrated Radiance after the radiometric correctionCalibrated Radiance after the radiometric correctionScaled Reflectance with atmospheric correctionScaled Reflectance with atmospheric correction

IPFIPF ALOS/AVNIR2ALOS/AVNIR2

AVNIR2 Instrument Process FacilityAVNIR2 Instrument Process Facility

While we were developing the image processor, we began to assemble the IPF. While we were developing the image processor, we began to assemble the IPF.

•simplified model for calculating reflectance not sufficient

•accurate reflectance crucial for generation of realistic images

•simplified model for calculating reflectance not sufficient

•accurate reflectance crucial for generation of realistic images

To reduce the reflectance calculation errors, radiance needs to be very precise.To reduce the reflectance calculation errors, radiance needs to be very precise.

Our IPF today generates radiances identical on a binary level to those of the reference IPF.Our IPF today generates radiances identical on a binary level to those of the reference IPF.

IPFIPF ALOS/AVNIR2ALOS/AVNIR2

AVNIR2 Instrument Process FacilityAVNIR2 Instrument Process Facility

IPF can generate the following products:IPF can generate the following products:

•Level1A generation from raw data•Level1A generation from raw data

IPF is able to process from raw data up to a Level1B scene in less than 30 seconds. IPF is able to process from raw data up to a Level1B scene in less than 30 seconds.

Processing can be performed:• by scene (nominal)• in stripline mode

Processing can be performed:• by scene (nominal)• in stripline mode

•Level1B generation from Level1A•Level1B generation from Level1A

•Level2 generation from Level1B (under validation)•Level2 generation from Level1B (under validation)