The PRISMA space segment consists in a single small class spacecraft, with a mass of about 830 kg, placed on a frozen sun synchronous orbit with a repeat cycle of 29 days (430 orbits). The orbit mean altitude is about 614,8 Km with an inclination of 97.851°. The Local Time of Descending Node is 10.30 AM.
The PRISMA payload is a hyperspectral/panchromatic camera with VNIR (Visible and Near-InfraRed) and SWIR (ShortWave InfraRed) detectors. It consists of an Imaging Spectrometer, able to acquire in a continuum of spectral bands ranging from 400 to 2500 nm, and a medium resolution Panchromatic Camera (PAN).
The hyperspectral sensor with a Ground Sampling Distance (GSD) of 30 m will cover the wavelength range from 400 nm to 2500 nm, with 10 nm spectral sampling through two partially overlapped spectrometers. The panchromatic camera instead will acquire the same area with a spatial resolution of 5 m GSD.
The PRISMA Hyperspectral sensor utilizes the prism to obtain the dispersion of incoming radiation on a 2-D matrix detectors in order to acquire several spectral bands of the same ground strip. The “instantaneous” spectral and spatial dimensions (across track) of the spectral cube are given directly by the 2-D detectors, while the “temporal” dimension (along track) is given by the satellite motion (pushbroom scanning concept).
The PDHT will store the acquired data in its internal memory and download it to the ground station in Matera via a dedicated X-band link.
The PRISMA GS consists of the following main elements:
MCC – Mission Control Center
SCC – Satellite Control Center
IDHS - Image Data Handling Segment/Center
The MCC consists of a unique subsystem, the Mission Planning System (MPS). It is the G/S element responsible for the scheduling of on board operations and for coordinating ground activities, performing overall mission planning, allocating resources and solving conflicts. Its objective is to produce a conflict-free plan of activities for the near future time span, which achieve the users acquisition requests and optimize system performances.
The SCC includes the Satellite Control System (SCS), the Flight Dynamics System (FDS), the S-band TT&C Station (TT&C) and the G/S Network (Communication infrastructure connecting the PRISMA G/S centers and facilities).
The IDHS is in charge of performing all the chain from the Users requests management to the delivery of final products, including reception of images data from the satellite and their processing. It includes different elements:
- Centro Nazionale Multimissione (CNM)
- L0 Processor
- L1 Processor
- L2 Processor
- Calibration facility
- GCP DB.
The CNM at the ASI Matera Space Centre, provides all ground segment functions related to catalogue browsing, image ordering from catalogue, standard products processing and product delivery. It includes the X-band ground station used to receive the payload data downloaded by the PRISMA satellite.
The user will access the PRISMA services via web through a unique access point named CNM Access System (CAS) permitting a Single Sign-On (SSO) authentication and then the access to the User Interaction Subsystem (UIS). The UIS provides end users with web-based interfaces for user management, accessing services relevant to catalogue browsing and query, products ordering, processing requests and help desk. Users can order the following new acquisition or catalogue products:
- TOA (Top Of Atmosphere) radiometrically and geometrically calibrated HYP and PAN radiance images
- Geolocated and Geocoded Atmospherically corrected HYP and PAN reflectance images.