Progress of in-flight Calibration of HJ-1A/HSI Li Chuanrong Invited expert of NRSCC Professor and Vice President Academy of Opto-Electronics,CAS Phuket, Nov 03, rd CEOS Plenary I Phuket, Thailand I 3-5 December 2009

Contents Brief introduction of HJ satellite and HSI senor CAL/VAL activities of HJ-1A/HSI Challenges Prospect 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December 20092

Introduction 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December “2+1” 2 optical moonlets 1 radar-moonlet first-stage “4+4” 4 optical satellites 4 radar satellites second-stage On , the small satellite constellation HJ -1A/1B were launched by a single LM-2C (CZ-2C) launch vehicle. On , HJ -1A/1B were ready for operational applications. HJ -1C will launch soon.

Introduction 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December satelliteHJ-1AHJ-1B payload 2 CCDs HSIIRS orbital typesun-synchronous orbit orbital height （ km ） orbital inclination orbital period (minute) circles per day14+23/31 revisiting period (hour) CCD96 (48 with HJ-1A/1B combination) HSI96 IRS96 coverage period (day)31 coverage period circles457 local time at descending node10:30 AM ± 30min

The small satellite for environment and disaster ( HJ- 1A) in China carried a hyper- Spectral Imaging (HSI) sensor, designed by Academy of Sciences, CAS HJ-1A Spectral range: 450nm-950nm Band number: 115 Spatial resolution: 100m Swath: 50km Side-looking: ±30° Revisiting: 4-31days Introduction

Principles of HSI 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December  The imaging approach used by HSI is a spatially modulated Fourier transform method based on a Sagnac interferometer.  Onboard inner calibration mode and earth observation mode can be switched by a swing mirror. Introduction

23 rd CEOS Plenary I Phuket, Thailand I 3-5 December Principles of HSI Introduction

Imaging Parameters of HSI Parameters HJ-1AEO-1 CCDHSIALIHyperion Spectral Range nm nm nm nm Spatial Resolution30m100m30m Swath Width360km50km36km7.5km Spectral Resolution--~4.3nm--~10nm Number of Bands Comparison of Parameters Between HJ-1A and EO-1 Introduction 8 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December 2009

Calibration requirement to HSI:  New imaging system and mechanism — We have less experiences  We have not carried out on board calibration with consideration of instrument safety  With the issues above we do need more sites and more experiments to study the way to calibrate this new kind of sensor CAL/VAL activities of HJ-1A/HSI 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December 20099

Vicarious calibration activities Dunhuang Site (twice after launch) – 40.08N, E – Altitude: 1200m – (Gain level 1) – (Gain level 2) Inner Mongolia (once for validation) – rd CEOS Plenary I Phuket, Thailand I 3-5 December CAL/VAL activities of HJ-1A/HSI

Measure Target Surface Properties Measure Atmospheric Properties Radiative Transfer Model - Modtran; 6S Predicted At-Sensor Radiance (L) Illumination + Viewing angles Sensor Signal (DN) DN L Gain=dL/dDN offset Sensor’s spectral response function Vicarious calibration at Dunhuang Site 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December

Radiometric vicarious calibration results of HSI （ Gain1) WL(nm)GainWL(nm)GainWL(nm)GainWL(nm)GainWL(nm)Gain

Cross comparison at Dunhuang site Between HJ-1A/HSI channels and corresponding MODIS bands 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December

HJ-1A/HSI and Terra/MODIS Image Pairs MODIS channel 1 UTM 04:25 May 29,2009 HSI channel 73 UTM 04:41, May 29, pixels 180 pixels Cross-comparison at Dunhuang site 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December CAL/VAL activities of HJ-1A/HSI

MODIS channel 1HSI channels MODIS channel 2HSI channels MODIS channel 3HSI channels 1-11 MODIS channel 4HSI channels rd CEOS Plenary I Phuket, Thailand I 3-5 December Cross-comparison at Dunhuang site CAL/VAL activities of HJ-1A/HSI

MODIS observed radianceHSI-convolved radiance MODIS channel MODIS channel MODIS channel MODIS channel distinction of observing geometry and atmosphere due to different acquisition time Discrepancy MODIS calibration accuracy HSI calibration accuracy Cross-comparison at Dunhuang site CAL/VAL activities of HJ-1A/HSI

Current challenges  Uncertainties in radiometric vicarious calibration  Radiometric cross-calibration method based on other well-calibrated satellite data is to be studied  Spectral calibration is to be expected 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December

Prospect  Invited by former WGCV group chair Dr. Cao Changyong, we will take part in Antarctic Dome C project on behalf of NRSCC  The actions including confirmation of coverage area of Antarctic region and planning of data acquisition in Dec. of this year has been carried out  By working on this project, AOE, as technical and operational facilitator of NRSCC, is willing to join the actions of CEOS WGCV.  AOE will also be pleasant to technically bridge the action cooperation between CEOS and China related agencies, such as data democracy, calibration, validation, virtual constellation etc. 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December

Anticipated agency participation HJ-1A/HSI image over Dome C area for example 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December :59 scene Center Latitude: S ° scene Center Longitude:E ° solar altitude angle: 5.5°

Anticipated agency participation Near-term plans  Provide related HJ-1A/HSI data and technical parameters support, so as to enrich datasets about the Dome C site.  In accordance with the procedure of CEOS/WGCV, carry out the cross-calibration studies between HJ-1A/HSI and other well-calibrated visible/near infrared sensors based on the Antarctic Dome C calibration site.  Invite foreign calibration experts including those work for CEOS to go to China for scientific discussion periodically. 23 rd CEOS Plenary I Phuket, Thailand I 3-5 December

Thank you !