GEMS Mission Overview and Status

Jhoon Kim1, P.I., GEMS,

U. Jeong1, M Kim1, D.H. Ko2, S. Go1, M. Eo3, M.H. Ahn3,

X. Liu4, K. Chance4, P.K. Bhartia5, P. Veefkind6, D. Nick7 & GEMS Science Team 1 Yonsei Univ, Seoul, Korea, 2KARI, 3Ewha WU, 4Harvard Smithonian CfA, 5NASA; 6KNMI, 7BATC

OMI STM 20, NASA GSFC, Greenbelt, MD, Sep 11th, 2017

Ima

ge

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dit, N

AS

A L

aR

C

A Day in the Life of the Constellation: May 31

Courtesy,

Ben Veihelmann

2

GEMS (2019)

Sentinel-4(2021)

TEMPO(2018-2021)

w/TROPOMI@ LEO

Duncan et al. (JGR, 2016)

Long-term NO2 trends seen by OMI

GK-2 Payloads

(Courtesy, KARI)

<

GEMS

5

y(t)

λ

N

S

Spatial Resolution Comparisons

GOME

GOME-2

SCIAMACHYOMI

GEMS

City Coverage of GEMS in Asia

Seoul Pyungyang Beijing

Shanghai Hebei Tokyo

Bangkok Singapore Taipei

7

(U. Jeong, 2015)

Product Importan

ce

Min

(cm-2)

Max

(cm-2)

Nominal

(cm-2)

Accurac

y

Window

(nm)

Spat Resol

(km2)@Seo

ul

SZA

(deg)

Algo-

rithm

NO2

O3

precursor3x1013 1x1017 1x1014 1x1015

cm-2 425-4507 x 8

x 2 pixels< 70

DFDOASPCA

SO2

Aerosol

precursor

Volcano

6x108 1x1017 6x1014 1x1016

cm-2 310-330

7 x 8

x 4 pixels

x 3 hours

< 50

(60*)

HCHOVOC

proxy

1x1015 3x1016 3x1015 1x1016

cm-2 327-3577 x 8

x 4 pixels

< 50

(60*)

CHOCHO 1x1014 1x1015 5x1014 1x1015

cm-2 437-452 7 x 8 x 4 px < 50

TropLO3TropUO3

StratO3

TotalO3

Oxidant

Pollutant

O3 layer

4x1017 2x1018 1x1018

3%(TOz)

5%(Stra)

20(Trop)

300-340 7 x 8 < 70OETOMS

AOD

AI

SSA

AEH

Air quality

Climate0 (AOD) 5 (AOD) 0.2 (AOD)

20% or

0.1@

400nm

300-500 3.5 x 8 < 70

Multi-l

O2O2

[Clouds]

ECF

CCP

Retrieval

Climate0 (COD) 50 (COD) 17 (COD) 300-500 7 x 8 < 70

O2O2

RRS

Surface

Property

Environ-

ment0 1 - 300-500 3.5 x 8 < 70

Multi-l

UVIPublic

health0 12 - 7 x 8 < 70

GEMS Products (16)

GEMS Instrument Flight Model• Step-and-stare UV-Vis imaging spectrometer scanning at least 8/day in 30 min

• Daily solar and dark calibration

• Images coadded at each position + mirror move back < 30 minutes

• Diffusers for on-orbit solar calibration and onboard LED light source

Preflight characterization and environmental tests ongoing, to be delivered in Nov., 2017

(Court

esy

, KARI /

BATC

)

OpticalAlignment

for Spatial Test

Thermal panel and CMA Installation

GEMS Status

• Budget & Schedule– Science Team Grant renewed and budget secured until 2020

– 8th GEMS STM, Seoul, Korea, Sep. 25-27th, 2017

– PSR, Nov., 2017

– Delivery, Nov., 2017

– AIT at KARI, 2017-2019

– Launch, Mar., 2019

• GK-2B System AIT Schedules at KARI– Bus I&T : ~ Nov. 2017

– Payload I&T : Dec. 2017 – Feb. 2018

– Antenna I&T : Mar – Apr. 2018

– Thermal Vac test : May – Jul 2018

– SA I&T : Jul – Aug 2018

– Dynamic Test : Aug – Oct 2018

– EMC Test : Nov 2018

– Final Preparation : Dec 2018

– Launch Campaign : Feb – Mar 2019

Preflight Characterization

• Bandpass– 301.8, 330.0, 365.0, 390.0, 435.0, 470.0, 498.2 nm;

– for N-S pixels

• BTDF– 300, 315, 325,350, 375, 400, 425, 500 nm;

– field positions at 0, +1.93, +3,87 deg, uncertainty(1s) less than 0.13 %

– Full spectral resolution measurements of transmission for the witness diffuser

• Straylight : – broadband characterization,

– PSF : Much higher dependence in spectral direction than spatial.

• Spectral Performance tests– keystone, smile, band width, spectral sampling, spectral calibration

• Linearity tests etc.

• Polarization, MTF, spatial performance, radiometric performance etc.

L0-1 Processor

• Earth, Solar ObservationsL0 Earth Input

(2112 * 1068)

Hot/Dead/RTS Pixel Flagging

(2112 * 1068)

Co-addition Correction

(2112 * 1068)

Gain/Offset Correction

(2112 * 1068)

Non-linearity Correction

(2112 * 1068)

Dark Correction

(2112 * 1068)

Smear Correction

(2112 * 1068)

QE/PRNU/Integration Time

(2048 * 1032)

Stray light

(2048 * 1032)

Radiometric Calibration

(2048 * 1032)

L1B-Earth

(2048 * 1032)

Spatial Registration

(2048 * 2)

Spectral Calibration(TBD)

(2048 * 2)

L0 Solar Input

(2112 * 1068)

Hot/Dead/RTS Pixel Flagging

(2112 * 1068)

Co-addition Correction

(2112 * 1068)

Gain/Offset Correction

(2112 * 1068)

Non-linearity Correction

(2112 * 1068)

Dark Correction

(2112 * 1068)

Smear Correction

(2112 * 1068)

QE/PRNU/Integration Time

(2048 * 1032)

Stray light

(2048 * 1032)

BTDF/Goniometry/Irradiance

(2048 * 1032)

L1B-Solar

(2048 * 1032)

Spatial Registration

(2048 * 1)

L0 Solar Dark Input

(2112 * 1068)

Hot/Dead/RTS Pixel Flagging

(2112 * 1068)

Co-addition Correction

(2112 * 1068)

Gain/Offset Correction

(2112 * 1068)

Non-linearity Correction

(2112 * 1068)

Earth Spatial Registration

– Lat. And Long. Assignment of

a center of the pixels (2048 * 2)

Solar Spatial Registration

– Pixel Solar Zenith Angle (2048 * 1)

Spectral Calibration

- Squeeze, Shift values (2048 * 2)

(Input to ‘Spectral Shift’ in ‘On-Orbit Calibration’)

(Courtesy, KARI / BATC)

L0-1 Processor

• Under development by BATC & KARI

• Dark correction :

- fitting by temperature changes added

• Smear correction :

- ratio of frame transfer time to integration time, with previous

frame effects considered

• Straylight correction :

- matrix, Richardson-Lucy deconvolution, but computing time issue

• Spectral correction :

- Reference solar spectrum convolved with GEMS bandpass

functions, polynomial equation

• Onboard LED calibration :

- for linearity, gain and PRNU(TBD)

• Polarization correction :

- VLIDORT, Linear polarization sensitivity tests, LUT in

collaboration with TEMPO team

Polarization Correction

Scan direction

(Ukkyo Jeong)

L1-2 Processor

Beta version of L1-2 algorithm

Algorithm review and accuracy evaluation (2017.6),

Now in 2nd Phase to upgrade and optimize for installation at GEMS Ground Station

ATBD review and ver 0 (2017.3)

Interface between L0-1 & L1-2, with consideration of preflight test results

NRT Operation Tests at NIER

Unified algorithm under test environment

- AOD, CLD algorithm at Server 3

- Ozone algorithm at Server 1,2,3,4

- HCHO, NO2, SO2 algorithm at Server 3

Migration to GEMS Ground Station at NIER

SO2

HCHO

CHOCHO

Sulfur Dioxide

Formaldehyde

Glyoxal

SO2

HCHO

CHOCHO

(Courtesy, InSpace)

Examples of retrieved products using OMI

16

Troposp. O3 O3 profile HCHONO2

GCA ECF1

0

GCA CP

Credit :

Mijin Kim (Yonsei U) – Aerosol

Y.S. Choi (EWU) - Cloud

Jae H. Kim (Busan NU) – O3

Hanlim Lee (Pukyung NU) - NO2

Rokjin Park (SNU) – HCHO, CHOCHO

Y.J. Kim (GIST) –SO2

J.M. Yoo(EWU), M.J. Jeong(GWNU) – Sfc prod

M.H. Ahn (EWU) - calibration

AOD SSAAerosolHeight CHOCHO

Comparison of GEMS Algorithm Accuracy

5th evaluation

(2017.3)

Correlation

coefficient

(R)

a, Slope b, Intercept RMSE Error (%) Remark

O3 (Total) 0.97 0.955 5.4 DU 2.35% -Brewer Spectro-

photometer

O3 (Trop) 0.79 0.89 1.91 DU6.48 DU

(10-20%)2 DU (7.29%) Ozonesonde

HCHO

0.82~0.84

(MAM/JJA/SON)

0.49 (DJF)

1.06 – 1.23 -2.6-5.2 x 1015 - - OMI Products

NO2 0.98 1.2 1.2 x1015cm-2 N/A 20% OMI Products

SO2

0.98

0.87 (<10 DU)

0.88 (<20DU)

0.4

0.39

0.40

0.06 DU

0.09 DU

0.06 DU

N/A

53.5 %

64.1 %

56.4%

OMI Products

Airborne

ECF 0.99 1.0 0.03 0.06 - OMI Products

CP 0.89 0.97 -30 95 - OMI Products

Surface

Reflectance0.87 N/A N/A 0.01 5~40% OMI Products

AOD 0.72

0.45(HA)

0.73(Dust)

1.25(NA)

N/A N/AQ-value : 33.2 ~

54.2%AERONET

The presence of aerosol layer at higher altitude

results in larger errors in NO2 VCD up to ~60%.

Lower SSA of aerosol than true value results in

the underestimation of NO2 VCD.

NO2 VCD changes due to AMF error with the presence

of aerosol

Further work is underway to separate tropospheric and stratospheric VCDs, by

using NO2 vertical profiles from CTM and the method of Buscela et al. (AMT

2013).

Hong et al. (RS, 2017)

19

May 17 Morning

NO2 SO2HCHO

GeoTASO trace gas retrieval during KORUS-AQ Campaign

Pandora: Circle

GeoTASO: Shaded

Temporal collocation: Average Pandora data

within ±5 min from GeoTASO overpass time

[Courtesy of Hyunkee Hong,Hanlim Lee et al.]

Courtesy, Scott Janz, MattKowalewski,

Jay Al-Saadi, Heesung Chog, Seoyoung Lee

PC

AD

F/D

OA

S

GEMS Ground Station at NIER

• Building to be completed by Oct. 2017

• Receiving and processing system to be installed by Mar. 2018

Summary

• GEMS flight model is under the final tests before its delivery to KARI i

n Nov. 2017.

• L0-1 and L1-2 algorithms are under the development to be ready for t

he launch of GEMS in March 2019.

• L1-2 algorithm for gases and aerosols show reasonable

performances, but requires further improvement, including hourly

retrieval in AMF, S/T separation in particular.

• Careful consideration of aerosol is required to retrieve trace gas

concentration from geostationary satellite remote sensing, especially

for absorbing aerosols at lofted altitude in particular.

• Preflight test results to characterize stray light, polarization, spectral accuracy,

diffuser BTDF, dark current etc. can provide more accurate analysis on the

GEMS performance and L2 algorithm.

• Synergy with AMI and GOCI-2 will provide more reliable products of aerosol

and cloud products, which eventually improve the accuracy of trace gas

column density.

Acknowledgement

GEMS Science Team

Ministry of Environment (MoE)

NIER, MoE

KEITI, MoE

Korea Meteorological Administration (KMA)

Korea Ocean R&D Institute (KORDI)

Ministry of Science, ICT & future Planning (MSIP)

KARI

GEMS Science TeamMyung Hwan Ahn

Yong Sang Choi

Myeongjae Jeong

Jae Hwan Kim

Young Joon Kim

Hanlim Lee

Kwang Mog Lee

Kwon Ho Lee

Rokjin Park

Seon Ki Park

Chang Keun Song

Chul Han Song

Jung Hun Woo

Jung-Moon Yoo

Changwoo Ahn

Jay Al-Saadi

P.K. Bhartia

Kevin Bowman

Greg Carmichael

Kelly Chance

Mian Chin

Yunsoo Choi

Ron Cohen

Russ Dickerson

David Edwards

Annmarie Eldering

Dave Haffners

Ernest Hilsenrath

Daneil Jacob

Scott Janz

Glen Jaross

Siwan Kim

Thomas Kurosu

Barry Lefer

Qinbin Li

Beri Ahlers

Heinrich Bovensmann

John Burrows

Marcel Dobber

Joerg Langen

Pieternel Levelt

Ulrich Platt

Piet Stamnes

Nicholas Theys

Pepijn Veefkind

Ben Veihelmann

Thomas Wagner Hajime Akimoto

Sachiko

Hayashida

Hitoshi Irie

Yasko Kasai

Kawakami Shuji

Alexis Lau

Jintai Lin

Charles Wong

Xiong Liu

Randall Martin

Steve Massie

Jack McConnel*

Tom McElroy

Jessica Neu

Mike Newchurch

Stan Sander

Jochen Stutz

Omar Torres

Dong Wu

Liang Xu

Ping Yang

Dusanka Zupanski

Milija Zupanski

Sang-kyoon Kim

Lim Seok Chang

Jae-Hyun Lim

K.J. Moon

M.H. Lee

H.W. Seo

Sukjo Lee

Jin Seok Han

Youdeog Hong

Ji-hyung Hong

J.S. Kim

Seung Hoon Lee

Sang Soon Yong

D.G. Lee

J.P. Gong

Dai Ho Ko

S.H. Kim

J.H. Yeon

Y.C. Youk

…Mijin Kim, Ukkyo Jeong, S.J. Ko, Sangseo Park, M.J. Choi, J.H. Kim, H.S. Chong, Se; Ju

Seon Bak, Kanghyun Baek; Hyeong-Ahn Kwon, H.J. Cho; K.M. Han, Jihyo Chong, Kwanchul

Kim; J.H. Park, Y.J. Lee …, Bo-Ram Kim, M.A. Kang, J.H. Yang, Sujeong Lim, S.W. Jeong ;

Thank you