Remote Sensing

Operationalisation of Thunderstorm Nowcasting Services over NE Region using DWR data

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North Eastern Space Applications Centre (NESAC) has been providing thunderstorm nowcasting (forecasting up to 4 hours) services for North Eastern Region (NER) of India since 2015 under the North Eastern Regional node for Disaster Risk Reduction (NER-DRR) initiatives. This was done using the data from satellite imager and sounder onboard INSAT-3D / INSAT-3DR, automatic weather station data, and by analysing numerical weather forecast data. However, it was difficult to detect, track and forecast using this data alone as most of the thunderstorms being a localised event, extending only over a few tens of km and having a lifetime of less than one hour. The availability of DWR data has opened a new window for precise identification of thunderstorm weather systems, track them and forecast the probable areas which may get affected, albeit with lesser lead time.

The first S-band dual-polarimetric Doppler Weather Radar (DWR) was installed at Cherrapunjee, Meghalaya which was dedicated to the nation by Shri Narendra Modi, Hon’ble Prime Minister of India on May 27, 2016. NESAC is operating the DWR continuously since then, and the data is made available in near real-time for the public through the MOSDAC (Meteorological and Oceanographic data archival centre) and IMD websites. The DWR is calibrated at regular intervals and the data and products are being validated. It has unobstructed coverage for the entire state of Meghalaya, Tripura, Southern Assam, and part of Mizoram and Manipur. For the western and central Assam region, the DWR has coverage beyond 3-degree elevation only. The DWR also sees a large part of India’s neighbouring country, Bangladesh. The radar completes one volume scan in 11 minutes, comprising of 360-degree azimuth scan for 10 elevation angles ranging from 0.5 to 21 degrees. It also allows sector scan (in both azimuth and elevation) for high temporal observation of any event. The DWR covers a distance of 250 km (up to 500 km only for Z) with a spatial resolution of 300 m.

A thunderstorm is a pre-monsoon season (April-May) phenomenon over the NER of India. The data collected by the DWR during 2016 was used to understand the thunderstorm and storm signatures and calibrate the nowcasting model. During 2017 the nowcasting service was made operational. Severe thunderstorm nowcasting services for Southern Assam, Meghalaya, and Tripura were done primarily using the DWR data and for the rest of the NER, the earlier methodology was used. In addition to the Z (radar reflectivity), S (spectral width) and V (velocity) data collected by the DWR, extensive use of the polarimetric data like ZDR (differential reflectivity) and ρHV (Correlation coefficient) were also made to differentiate thunderstorm clouds from non-thunderstorm clouds.

The use of the Cherrapunjee DWR data has improved the thunderstorm nowcasting accuracy over Meghalaya, Southern Assam, and Tripura states. Altogether 48 severe and very severe thunderstorms were forecasted in these three states during April 1 to June 15, 2017, period. The accuracy of nowcasting was more than 90% with lead time varying from 30 minutes to more than 2 hours. The nowcasting services were disseminated through NER-DRR website and also through direct communication to the concerned at the state level.

NESAC DWR  NESAC DWR

(The DWR, Cherrapunjee coverage for an elevation angle of 3 degrees (left). Calibration of the DWR using metal sphere attached to hydrogen gas-filled balloon & Pisharoty sonde (right))

 Max V data from DWR, Cherrapunjee. Max V is used to estimate the velocity at which a weather system is moving Max S data from DWR, Cherrapunjee. Max S gives an idea about the internal turbulence within cloud system

(Max V (left) and Max S (right) data from DWR, Cherrapunjee. Max V is used to estimate the velocity at which a weather system is moving and Max S gives an idea about the internal turbulence within cloud system)

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ISRO Developed Haze Removal Algorithm for Cartosat Images

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High-resolution optical imaging Earth Observation Satellite (EOS) systems such as CARTOSAT provide multi-spectral remote sensing data in the visible and near-infrared (VNIR) wavelengths of the order of sub-meter to few-meters. These datasets can be used in a variety of applications, particularly associated with precise mapping, monitoring and change detection of earth’s surface, if top of the atmosphere (TOA) measurements can be properly compensated for atmospheric absorption and scattering effects. Existing physics based atmospheric correction (AC) algorithms for multi/hyperspectral remote sensing data over land involves simultaneous use of visible and short-wave infrared (SWIR) channels to derive aerosol information. Hence, such algorithms cannot be used for AC of data acquired by VNIR sensors to derive “surface reflectance”.

Towards this, Space Applications Centre, Ahmedabad has developed a new algorithm for AC of high-resolution VNIR remote sensing data in which aerosol information is retrieved from sensor measurements in VNIR channels and by selecting appropriate aerosol optical properties from a set of defined aerosol models. The algorithm uses lookup tables generated with vector radiative transfer calculations. Derived aerosol information and pre-computed lookup tables are employed to derive surface reflectance.  Good quality surface reflectances have been obtained when this algorithm was applied on Cartosat-2 Series Satellite data. It is found that this algorithm significantly removes the haze from the images, making surface features distinctly visible, and hence more useable for qualitative as well as quantitative analysis and further applications.

Following figures illustrate the drastically improved quality of the images after applying the AC algorithms, where the contribution of light due to molecular scattering and scattering from thick layer of aerosol to the sensor measurement at the top the of the atmosphere is removed.

Top of the Atmosphere reflectance

Atmospherically corrected reflectance

(Parts of Ahmedabad as viewed from Cartosat-2 Series Satellite on 03/11/2016)

Cartosat-2 Series Satellite View of Ahmedabad , Satellite Area on 03/11/2016

(Cartosat-2 Series Satellite View of Ahmedabad, Satellite Area on 03/11/2016)

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Space Application Centre

Visualizing the Changing Planet with Landsat Explorer Web App

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The new Landsat Explorer web app from Esri enables users to wield Landsat imagery to explore geology, vegetation, agriculture, and cities anywhere in the world. The app, driven by publicly accessible image services, offers a way to better visualize the planet and understand how the earth has changed over time.

(A false color band combination, where vegetation appears in red, delineates the Exumas Islands in the Bahamas. With the Scatter Plot tool, users can select two bands to plot on a graph, with the more frequent occurrences appearing on this graph in red.)

Using the app is simple: Open it in a web browser, search for a location, and apply analysis tools on the fly to get immediate, dynamic results. With no download required, Landsat Explorer users get instant, interactive access to an extensive collection of multispectral, multi temporal Landsat imagery.

Landsat satellites have been collecting information about the earth’s surface for almost 45 years. Each Landsat image contains multiple bands of spectral data gathered at different wavelengths. More than just offering pictures of the planet, Landsat’s different bands can be combined and analyzed to learn about what is happening on the ground, beyond what the eye can see.

Beyond enabling users to instantly view half a million Landsat images using different band combinations or enhancements, Landsat Explorer offers extensive analytical capabilities. The visualization and analysis tools let users do the following, all on the spot:

  • Visualize the data using custom indexes and band combinations
  • Filter and select specific dates to analyze and compare
  • Interactively compare two images using a swipe tool
  • Create custom masks
  • Perform change detection
  • Generate spectral and temporal profiles
  • Create scatter plots using spectral bands
  • Add data (city roads, for example) from ArcGIS Online

Landsat Explorer joins Esri’s existing suite of Landsat apps, including the Landsat Arctic and Antarctic Apps. Whether users answer their own questions by applying Landsat Explorer’s powerful analysis tools or take the small leap to create their own imagery apps, it’s never been simpler to instantly visualize and dynamically analyze the earth’s surface.

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Landsat Explorer

BRICS Nations Agreed to share spatial data from Remote Sensing satellite

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Member nations of the five-nation group BRICS have agreed to share spatial data on natural resources from their remote-sensing satellites.

The move is geared towards making optimal use of space assets. According to Indian Space Research Organisation (ISRO) officials the nations will be exchanging data, including images of natural resources. Though only four of them – Brazil, Russia, India and China have remote-sensing satellites in the sun-synchronous orbit, they will give data to South Africa (SA) as it does not have a satellite of its own. Top space officials of BRICS met at the United Nations Committee on the Peaceful Uses of Outer Space Scientific and Technical Subcommittee’s 54th session at Vienna in Austria from January 30 to February 10.

Through this particular agreement, BRICS will be able to share the resources and bring developing nations under the umbrella of space, opening possibilities of using excess capacities in the satellites. As the BRIC satellites spin around the earth in lower orbit, capturing enormous data on the planet and its resources in each country, they will share it in real time for mutual benefit.

India plans to use its Resourcesat-2A, launched on December 7 from its spaceport Sriharikota in Andhra Pradesh, as part of its earth observation satellite for remote sensing data services to global users.

Going forward, the space agencies of the BRICS nations plan to share similar data for tele-education, tele-medicine and a host of societal applications, utilising the excess capacity of their respective satellites for their mutual benefit.

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India’s most flood-prone state Bihar aided by new satellite mapping

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Every year Bihar is deluged by floods that submerge roads, destroy homes and wash away crops, leaving the disaster management authority struggling to monitor and assess the damage, and to distribute aid effectively. But new satellite mapping of flood-prone areas should transform disaster response by equipping authorities with near real-time information about inundated villages, officials said.

Bihar, which borders the Himalayan nation of Nepal, is India’s most flood-prone state. More than 70 percent of its total geographical area is at risk of annual floods, which put lives at risk and lead to heavy financial losses.

A major challenge for the Bihar state disaster management authority (BSDMA) has been mapping and monitoring flood-hit areas, according to the International Centre for Integrated Mountain Development (ICIMOD), which works to promote development across the Hindu Kush Himalayas.

Flood-affected villagers use temporary rafts as they navigate through the floodwaters of river Ganges and move to safer grounds, after heavy rains at Patna district in Bihar August 29, 2013.  REUTERS/Krishna Murari Kishan/Files

(Flood-affected villagers use temporary rafts as they navigate through the floodwaters of river Ganges and move to safer grounds, after heavy rains at Patna district in Bihar August 29, 2013. Credit: REUTERS)

Since floods started in the state last month, more than 200 people have died and more than 300,000 have been forced from their homes, disaster officials said. ICOMOD has helped generate innovative flood mapping for 33 districts in Bihar and an online flood information system that is allowing faster response to a crisis, quicker damage assessment, and better risk management than with conventional methods, said officials from ICIMOD, based in Kathmandu.

“Traditionally, field teams are organised and dispatched to flooded areas to map floods. This can be time-consuming and operationally difficult during a flooding event,” Shahriar M. Wahid, a senior ICIMOD hydrologist, told the Thomson Reuters Foundation via email.

While “satellite-sourced flood maps alone cannot provide early warning to (the) at-risk population”, he said, satellite data, in combination with flood simulations, can do this. If flash floods triggered by torrential rain occur in Nepal, Bihar’s residents can expect to see inundations about eight hours later, according to data from the BSDMA. Wahid said the new flood maps will be most useful for the distribution of relief, assessment of damages and to determine crop insurance payouts, among other benefits.

The project uses satellite technology that penetrates cloud cover, unlike optics-based satellite imagery. This is useful in the Himalayan region where monsoons bring thick clouds. Flood maps can be generated within five to six hours after raw satellite data is received. The floods are circulated to government officials and relief agencies through a satellite communication network. Space satellite technology is often touted by disaster relief experts as an important tool in managing the growing number of climate-linked disasters around the world. But the cost of such technology for developing countries, even fast-growing ones like India, can be a challenge.

Satellite maps can also aid prevention because they act as a template for years to come, recording rainfall patterns and data from the water department, among other factors, ICIMOD said.

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Koshi Basin Programme

First year data of Mars Orbiter Mission (MOM) released

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Chairman, ISRO and Secretary, Department of Space has released first year of MOM Long-term archive data (Sept 24, 2014 to Sept 23, 2015) to public.

India’s Mars Orbiter Mission (MOM) has successfully completed its designed life of 6 months on 24 March 2015 and accomplished its planned mission objectives.MOM is continuing to function normally and is completing two years around Mars on September 24, 2016. At present MOM and all its scientific payloads are in good health and it continues to provide valuable data of Mars surface and its atmosphere.

Mars Orbiter Mission is ISRO’s first interplanetary mission and is orbiting around Mars in an elliptical orbit of about 343 km x 71191 km as on 16th September 2016. Mars Orbiter Mission (MOM) is a complex technological mission considering the critical mission operations and stringent requirements on propulsion, communications and other bus systems of the spacecraft.

MOM carries a suite of five scientific payloads with a total mass of about 14 kg. The three payloads which have been designed, developed and delivered by Space Applications Centre are:

1. Mars Colour Camera (MCC)

2. Methane Sensor for Mars (MSM)

3. Thermal Infra-Red Imaging Spectrometer (TIS)

4. The Mars Exospheric Neutral Composition Analyzer (MENCA)

5. The Lyman-Alpha Photometer (LAP)

Snapshots from the portal:

Fig-1. Typical coverage data points MCC , TIS, MSM over Mars (Credit: ISRO)


Fig.-2. MSM Coverages

 

Online MOM data sets archive

The MOM archive will contain instrument raw data, derived or merged (wherever applicable) apart from spacecraft and instrument ancillary or housekeeping data. The MOM data sets are disseminated through an online archive, where the data are delivered electronically. A data set will include the instrument data as well as the ancillary data, software, and necessary documentation that support the use of these data products. In general, the data products from different instruments are contained in separate data sets. Data sets may include data products from one or separate data sets.

Acknowledge the source of data, funding etc.

Researchers and common public who is downloading the Mars Orbiter Mission data sets, are required to acknowledge the ISRO for data, funding (if granted) and the research writeups taken from the archive.

1. When publishing a paper using the Mars Orbiter Mission data, please

a) mention on “Mars Orbiter Mission (MOM)” in abstract and
b) include the following statement in acknowledgment –
“We acknowledge the use of data from the Mars Orbiter Mission (MOM), first inter-planetary mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC)”

2. If you are using the results of Mars Orbiter Mission which are already published and carrying out further interpretation or modeling, please include the following statement in acknowledgment

“The research is based partially / to a significant extent (whichever is applicable) on the results obtained from the Mars Orbiter Mission (MOM), first inter-planetary mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC)”

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Release Document

Browse Data

Mars Science Atlas

SCATSAT-1 – Satellite for Weather Forecasting, Cyclone Detection and Tracking

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Global wind data, which is very crucial for cyclone detection and weather forecasting applications, was gathered by Scatterometer instrument flown as one of the payloads in OCEANSAT- 2 satellite. This data was utilised by national and international users and proved to be a very important tool for oceanographic studies. SCATSAT-1 is the continuity mission for Scatterometer payload carried by the earlier Oceansat-2 satellite.

The magnitude and direction of the wind vector at the ocean surface is a key parameter for weather prediction as well as detection and tracking of cyclones. The objectives of SCATSAT-1 are to facilitate the weather forecasting services to the user communities through the generation of wind vector products. The Ku-band Scatterometer payload carried by SCATSAT-1 has enhanced features compared to the similar one carried by Oceansat-2 launched in 2009

Scatterometer operates on the principle of radar. When the radar radiates energy pulses towards the ocean’s surface, a backscatter effect is produced due to interaction between electromagnetic waves and sea surface waves, which is function of speed and direction of surface winds over the oceans.

This process of receiving back-scattered signal is carried out while conically scanning or rotating the antenna along with the motion of the satellite giving a swath of 1400 km. The collected data is processed onboard to generate estimates of backscattered power/signals and stored on a data recorder. This recorded data is then transmitted to ground station which is converted into wind vectors for the global user.

SCATSAT-1 is built around ISRO’s small satellite ‘IMS-2 BUS’ and the mass of the spacecraft is 371 kilograms. The spacecraft will work in sun synchronous orbit of 720 km. altitude with an inclination of 98.1 deg. This will be a polar orbiting satellite and will take two days to cover the entire globe. The expected life span of the satellite is 5 years with non-stop 24 X 7 all weather operations. Wind speed is measured in the range of 3m/s to 30m/s and 0-360 deg directions. Finally, wind vector grids of 25kms*25kms over oceans will be generated for the entire globe.

These wind vectors will help meteorologists in accurately predict the cyclone formation, its movement and estimated landfall. It may be recalled that Ocean wind vectors data helped in accurately predicting cyclone ‘Phailin’ in the Odisha coast in 2013, which helped in mitigation and saving of mankind and livestock.

SCATSAT-1 is a global mission and data generated from the Scatterometer, developed by ISRO will also be utilized by the American space agency NASA and European Space Agency organization, EUMETSAT to provide global weather data to all those involved in weather studies and global climate change studies.

Geospatial Network community congratulates ISRO scientists for this achievement.

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