Phenological Eyes Network (PEN)

--- Connecting Satellite Remote Sensing to the Ground-Level Ecosystems ---

What does PEN stand for?

Japanese / MPEG animation / gallery / open documents / closed documents / members / old news / links / development team / old page / paper list / presentation list /

Leaflet: PDF / PPT / JPEG (page1, page2, page3, page4)
Review article in AsiaFlux Newsletter (2007)

Note: Because many of the original information is in Japanese, you would obtain newer or more detailed infromation on Japanese main page.

Data request policy

If you have a plan to use PEN data for your presentation or article, please contact preliminarily. You also need to contact the site PI.


Science Daily News about AHS site.
BBC article about AHS site.
HVT site was established with a support by University of Hawaii.
YGT site was established with a support by Center for Environmental Remote Sensing, Chiba University.
PFA site was established with a support by JAMSTEC-IARC project.
UAK site was established with a support by JAMSTEC-IARC project.
AHS site was established with a support by UK-Japan project.
A new article referring to PEN in FluxLetter (p. 13-).
2005.2.27-7.6:We apologize that PEN mail-address for information and inquiry was out of order in this period.
2004.9.8:TFS site was encountered with Typhoon attack! The system of this site has been stoped.

Data of PEN

IDsite nameplant typedatanote
AHSAlice HoltDBFrecent original summary log2009-, ADFC. Managed by Forest Research and U. Edinburgh.
AI7AIST 7th Buildingurbanrecent original summary log2004 only. Sky ADFC only.
BDXBordeauxagricrecent original summary logADFC
EGTEGAT Tower, Thailandmixedrecent original summary log1999-2002. film camera only.
GDKGwangneungDBFrecent original summary log2009-, ADFC, HSSR
FHKFuji-HokurokuDNFrecent original summary log2005-, ADFC, HSSR, SP. Managed by NIES and AIST
FJYFuji-YoshidaENFrecent original summary log2009-, ADFC Managed by FFPRI
HVTHawaii Volcano ThurstonEBFrecent original summary log2012-, ADFC. Managed by U. Hawaii.
JNDJND,Chinarice paddyrecent original summary log2010-, ADFC. Managed by NIAES, JAMSTEC and U. Tsukuba.
KBFKranzberger forestDBFrecent original summary log2010-, ADFC Managed by Technical University of Munich.
KEWKiryu Experimental WatershedENFrecent original summary log2004-, ADFC, HSSR.
KFSBiyala, Kafr El Sheikh, Egypt (N31:10:16, E31:09:31) rice paddyrecent original summary log2011-, ADFC. Managed by U. Tsukuba.
KIZKaruizawaKIZrecent original summary log2009-, ADFC.
LAMOil palm plantationEvergreen plantation forestrecent original summary log2017-, Raspberrypi camera.
LBRLambir HillsEBFrecent original summary log2009-, ADFC.
MSEMase Flux siterice paddyrecent original summary log2005-, ADFC, HSSR. Managed by NIAES, U. Tsukuba, and AIST
MMFMoshiri Mixed Forest SiteMixed forestrecent original summary log2010-, ADFC. Managed by Hokkaido U. and U. Tsukuba
MTKMt. TsukubaMixed forestrecent original summary log2008-, ADFC; Tsukuba
PFAPoker Flat Research Range Fairbanks AlaskaECFrecent original summary log2011-, ADFC. Managed by JAMSTEC and IARC
SSPSpasskaya PadDNFrecent original summary log1997/08/25-2000/10/15, by Rikie Suzuki, JAMSTEC
RHNRIHNurbanrecent original summary log2005-2006. Sky ADFC only.
SGDSugadairagrasslandrecent original summary log2005-, ADFC. Managed by Tamagawa U.
SHASeoul Heonilleung Alnus ForestDecidious forestrecent original summary log2010-, ADFC.
TFSTomakomai Flux SiteDNFrecent original summary log2004. Destroyed by a typhoon. Managed by NIES.
TOCTomakomai Experimental Forest Crane siteDBFrecent original summary log2010- ADFC, HSSR. Managed by Gifu U., Hokkaido U. and NIES
TOETomakomai Experimental Forest Flux siteDNFrecent original summary log2010- ADFC, HSSR. Managed by Gifu U., Hokkaido U. and NIES
TOSTomakomai Satellite monitoring/validation siteDBFrecent original summary log2015- ADFC, HSSR. Managed by Hokkaido U. and U. Tsukuba
TGFTERC Grass Fieldgrasslandrecent original summary log2003-, ADFC, HSSR, SP. Managed by U. Tsukuba and AIST.
TKCTakayama Evergreen Coniferous SiteENFrecent original summary log2007-, ADFC, HSSR. Managed by Gifu U.
TKYTakayama Flux SiteDBFrecent original summary log2003-, ADFC, HSSR, SP. Managed by Gifu U., U. Tsukuba, and AIST.
TSETeshio CC-LaG Experiment SiteMixed forest, DNFrecent original summary log2006-, ADFC. Managed by Hokkaido U., U. Tsukuba and NIES
UAKUniversity of Alasla FairbanksECFrecent original summary log2010-, ADFC. Managed by JAMSTEC and IARC
URYUryu Experimental ForestSkyrecent original summary log2017-, ADFC. Managed by U. Hokkaido and Tsukuba U.
YGTYatsugatake SiteDNFrecent original summary log2011-, ADFC. Managed by JAMSTEC and Chiba University
3-character ID is taken from Asia/JapanFlux rule.
FJH has been renamed to FHK.
TFS has been renamed to TMK in Asia Flux community, but we still keep using TFS for convention.

* Acronyms: * Map of PEN sites

What is PEN?

Satellite remote sensing (RS) is a strong methodology in the study of terrestrial ecosystems. For example, RS is used in scaling up of the ground measurements of carbon flux, water flux, biomass, etc. from a site scale to a regional or global scale. RS provides numerical regional ecological models with information for initial conditions, boundary conditions, and validation. For the sake of it, various new satellite sensors have been designed and launched. They are now delivering a lot of high-level products regarding to the terrestrial ecology, such as new vegetation indices, LAI, FPAR, phenology, GPP, and NPP.

However, in the ecological standpoint, these RS methodology has not enough checked or validated on the ground level. Because an essential characteristics of ecosystem is its dynamism (especially the seasonal change, or "phenology"), the accuracy, quality, and interpretation of the RS data should be also studied dynamically. For the sake of it, a stable, continuous, long-term, and multi-ecosystem ground validation network is desired. Of course, the flux observation networks such as AsiaFlux have potential to contribute to it. However, because RS observes vegetation's optical characteristics rather than carbon or heat flux, we need to include optical (spectral) observation in the validation of ecological RS. We believe that the ecological interpretation of RS data is possible only if it is based on a careful theoretical and experimental study of the relationships between optical characteristics and ecological structure (or function), using the quality-controlled RS data considering the relevant noise factors such as cloud contamination or atmospheric aerosols.

With this background stated above, we have started the "Phenological Eyes Network (PEN; Tsuchida et al., 2005)." PEN is a network of ground observatories for long-term automatic observation of the vegetation dynamics (phenology), vegetation's optical properties (such as spectral reflectance), and the atmospheric optical properties (such as aerosol optical thickness). Most PEN ground sites have been set up at the AsiaFlux sites. The collaboration of PEN and AsiaFlux is critically important in the interpretation of the optical signals captured by RS in terms of ecology (especially the terrestrial carbon/water cycles).

PEN's scientific targets

PEN has been supported by the Global Environment Research Fund (S-1: Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific Advancement) of the Ministry of Environment of Japan.

Observation system

Because the goal of PEN is to collect long-term quality-controlled multi-site data, the main instruments should be stable, robust, and low-cost. Based on this principle, we selected and designed the following three types of instruments: the Automatic-capturing Digital Fisheye Camera (ADFC), the HemiSpherical Spectro-Radiometer (HSSR), and the sunphotometer (SP).


ADFC is a combination of a high-quality digital camera (Nikon CoolPix series), a fish-eye lens (Nikon FC-E8), a water-proof housing case, and a control system with a personal computer. It captures images of the sky, the canopy from above and below, the forest floor, and shoots of typical species with short intervals (2 minutes to 24 hours, depending on the target). These images provides information about cloud condition at the satellite's observation, vegetation phenology, snow pack, tree cover, and LAI.


HSSR is a hyper-spectral radiometer in the visible and near-infrared region (MS-700 of Eko Instruments Co. or PGP-100 of Prede Co.). In order to catch both incoming and reflecting radiation with a single radiometer, we developed a computer-controlled rotating stage in collaboration with Hayasaka Rikoh Co. If the HSSR is mounted on the rotating stage, it can be directed upward and downward consecutively with a short interval of time at a same position. Thus we can obtain the spectral features of the vegetation canopy with fine-temporal and fine-spectral resolution. By using such data, we can check the spectral observation of RS. Moreover, we can simulate various types of spectral indices (such as NDVI, EVI, PRI) with arbitrary spectral response of every specific satellite sensors.


SP is a spectral radiometer with a small field-of-view and pointing functionality. We use POM-02 of Prede Co. We can estimate optical properties of the atmosphere which are needed for atmospheric correction of the RS data. It can provide quantitative information about atmospheric pollution or aerosol dust (such as the Yellow Sands), both of which may have some direct or indirect impacts on the ecosystems.

Other sensors

In addition to the above-mentioned main instruments, in some sites, we are making observation of environmental ecophysiological properties including incoming PAR (direct and diffuse), transmitting PAR, leaf phenology, LAI (LAI-2000, fisheye image, laser profiler, and litter trap), leaf-level optics, leaf-level physiology (LI-6400, pigments, C/N, LMA).

Details on the system (in Japanese)

Data management system

Most data taken by these sites have been stored in the PEN's database server. The original data are open to the PEN community member (anybody can join if they want) and the summary or edited data are open to the public.


Presentations (except for Japanese)