PRISMA is the satellite mission funded by the Italian Space Agency with the aim of developing a satellite equipped with a new generation of hyperspectral optical sensor for observing Earth on a global scale.

While the currently operating satellite passive optical sensors record the solar radiation reflected from our planet in a limited number of spectral bands - typically at most a dozen - the sensor on board the PRISMA satellite is instead able to acquire 240 (239 spectral bands plus the panchromatic channel); this will allow to obtain information about not only geo-morphological structure but also the chemical and physical composition of the earth's surface.

Goal of the PRISMA mission is to provide scientific information is that more closely application type, for example in support of civil protection activities and environmental protection agencies.
Scientific part, PRISMA to help refine knowledge concerning natural resources and the main environmental processes in place, such as the phenomena linked to climate change. PRISM will provide information to support the study of processes and feedback mechanisms that interconnect the areas of our planet, such as the atmosphere, the biosphere and hydrosphere; changes of environment and climate globally; the effects of human activities on ecosystems; the availability of natural resources and environmental sustainability.
application context, PRISMA will be able to provide valuable information to support prevention works with respect to natural hazards (such as hydrogeological) and anthropogenic (including soil pollution), the monitoring of cultural heritage, of aid actions to humanitarian crises, from agriculture and exploitation of mineral resources.
This publication describes the main application outcomes of the mission, stating the subject - institutional and private - who will benefit from them for their work and highlighting the advantages and differences from existing satellite missions.
The PRISMA mission is developed in all its parts (space segment and ground segment) by a consortium of Italian companies led by OHB Italy SpA and LEONARDO Space & Airborne Systems.

Italy OHB is responsible for overall program management, planning, systems engineering, development and integration of the platform and all validation activities. LEONARDO is responsible for the design, development, integration, testing and calibration of hyperspectral sensor and panchromatic camera. The consortium includes, among others, Thales Alenia Space - Italy, responsible for the on-board system for the management and transmission of sensor data, Telespazio and ACS that deal with land dedicated to mission control and data processing segment at the Centre Multi-Mission ASI of Matera.

PRISMA Mission is based on the heritage gained in different space programs, as follows:

  • Payload reuses the heritage gained by Leonardo on Hypseo program
  • Payload Data Handling Unit is a re-use of the one currently in orbit on Cosmo-SkyMed
  • The Platform capitalizes the heritage gained by OHB-I on different programs i.e. MITA/AGILE, SAR-lupe
  • G/S Satellite Control Centre reuses the heritage gained on MITA/AGILE as well as Cosmo-SkyMed
  • G/S image data handling centre reuses ASI infrastructures i.e. Centro Nazionale Multimissione (CNM)

System Performance

Some of the System features are reported below:

  • Global coverage with constant 70°S - 70°N AOI performance
  • Maximum cross-track angle to observe ground track from: 21°
  • Orbit repetition cycle: 29 days
  • Maximum revisit time for a fixed ground target: 6 days
  • Acquisition latency, intended as the Maximum time from a specific acquisition request and its on-board availability: approx. 9 days
  • Processing latency, intended as the maximum time from on-board data availability of a single acquisition and the one for related associated products requested by the User: approx. 2 days
  • Earth surface which can be acquired in a single day: 200'000Km2, equivalent to about 223 30Km x 30Km spot images
  • The System is able to operate either in Spot Mode (30Kmx30Km) or in Strip Mode up until a maximum length of 1800 Km
  • System spot accuracy less than 1 Km
  • Geolocalization without GCP usage < 200m; with GCP < 15 m

 

 

The following table gives a general indication of the main parameters of the mission.

 

System Characteristics

 

Characteristic

Reference value

Note

Orbit

SSO 615 km 10:30 LTDN

Frozen orbit. Repetition Cycle: 29 days

Relook time

6 days

It is the worst-case value of revisit time for any ground target

Area of Interest

70° Nord ÷ 70° Sud

 

GSD

PAN = 5 m

HYP = 30 m

 

Spectral band

PAN: 0,4÷0,7 mm

VNIR: 0,4÷1,01 mm, 66 bande

SWIR: 0,92÷2,5 mm, 173 bande

 

Swath width

30 km

 

SNR

PAN > 240:1

VNIR > 200:1

SWIR > 200:1

 

MTF

PAN:

0.10 along-track a Nyquist

0.20 across-track a Nyquist

VNIR & SWIR: vedi tabelle seguenti

Typical MTF calculated at Nadir, depending on operational conditions and on production thresholds

Pixel size

PAN: 6,5 x 6,5 mm

HYP: 30 x 30 mm

 

Spectral sampling interval (SSI)

≤ 12 nm

 

Spectral width

≤ 12 nm

 

Absolute radiometric accuracy

Migliore del 5%

 

Off-nadir capability

±21 deg across track

 

Onboard Data Storage

448 Gbit

 

Downlink data rate

310 Mbps

Due canali in ridondanza calda

Acquisition and image downlink capability

200.000 km2/day

 

Potenza

~ 450 W

Average Power

Massa

~ 800 Kg

 

Capacità Sistema di Propulsione

118 m/s

Estimate of required capacity needed for acquisition and orbit maintainance < 90 m/s

Lifetime

5 years

 

Processing latency

< 2 days

Estimated latency time from data acquisition and Product delivery to the User

Pointing accuracy

< 1 km

 

  

System MTF for VNIR / SWIR channel

The following tables show the values of MTF (Modulation Transfer Function, an indicator of the quality of pictures taken) for each of two channels: VNIR (Visible and Near Infrared) and SWIR (Short Wave Infrared):

VNIR System MTF

   

Along-track

Across-track

 
 

Axial field

Marginal field

Axial field

Marginal field

0.4 μm

0.178

0.178

0.339

0.339

0.7 μm

0.179

0.18

0.341

0.342

1.01 μm

0.18

0.18

0.343

0.343

 

SWIR System MTF

   

Along-track

Across-track

 
 

Axial field

Marginal field

Axial field

Marginal field

0.92 μm

0.184

0.184

0.343

0.343

1.7 μm

0.184

0.184

0.343

0.343

2.5 μm

0.18

0.18

0.336

0.335

 

In the next two figures are shown instead of the signal to noise ratio value diagrams for all spectral bands of the instrument in some typical cases.

SNR dei canali VNIR e SWIR (VNIR typical case BOL)dei canali VNIR e SWIR (VNIR worst case EOL)

The figure below shows the time schedule of the final phase of the program until the launch and commissioning of the satellite and the resulting beginning of the mission.