INSAT-3 (Indian National Satellite-3) Series
The INSAT-3 series of ISRO (Indian Space Research Organization) is a multipurpose spacecraft with an all Ku-band transponder layout for direct-to-home television and roof-top data communication. The satellites incorporate state-of-the-art communication technology such as high power antennas, steerable beam and digital compression/decompression capabilities. The solar panel of the INSAT-3A spacecraft uses an advanced rigid deployable sun-oriented array of GaAs/Ge cells with an area of 26.5 m2.
Table 1: Overview of INSAT-3 satellite series (chronological order)
The description of the INSAT-3 spacecraft series focuses on the missions with meteorological payloads.
INSAT-3B is the first of the five satellites that was launched in the INSAT-3 series (built by ISRO). The satellite structure resembles a cuboid of 1.93 m x 1.7 m x 1.65 m and, with the two solar panels deployed (total area of 23 m2), it measures 14.7 m in length. The sun tracking solar panels generate 1.7 kW of power. A 24 Ah NiCd battery supports the payload operations during eclipses.
INSAT-3B is three-axis body-stabilized using momentum/reaction wheels, earth sensors, sun sensors, an inertial reference unit and magnetic torquers. It is equipped with unified bi-propellant thrusters. The satellite has two deployable antennas and three fixed antennas that carry out various transmit and receive functions. The antennas have a pointing accuracy of ±0.2º in pitch and roll axes, and ±0.4º in yaw axis. The satellite uses a passive thermal control system. 1)
The S/C mass is 2070 kg at launch, with 1100 kg of hydrazine propellant for orbit raising, station keeping and on-orbit attitude control. The S/C design life is 10 years.
Figure 1: Illustration of INSAT-3B (image credit: ISRO)
Launch: INSAT-3B was launched successfully on March 21, 2000 (UTC) from Kourou on an Ariane-5 vehicle (along with a passenger payload called Asia Star of the US company World Space), putting INSAT-3B into GTO (Geostationary Transfer Orbit).
The LAM (Liquid Apogee Motor), designed and developed by the Liquid Propulsion Systems Center, Thiruvananthapuram, India, took the spacecraft from GTO into GEO. For the first time, an indigenously developed titanium propellant tank, with special propellant management device that ensures bubble-free propellant supply under zero-G environment, has been employed.
Orbit: Geostationary orbit at 83º East, co-located with INSAT-2E.
The INSAT-3B communication payload provides 12 extended C-band channels, each having a bandwidth of 36 MHz. The Ku-band payload provides three channels, having a bandwidth of 77/72 MHz. The Mobile Satellite Service transponders operate in C/S band frequencies. Compared to INSAT-2C/2D, the power of extended C-band transponders on board INSAT-3B has been increased from 10 W to 15 W and that of Ku-band from 20 W to 55 W. - The INSAT spacecraft series missions are operated by the MCF (Master Control Facility) at Hassan in Karnataka, India. MCF has a network of six Satellite Control Earth Stations (SCES) to acquire its data.
INSAT-3A is a multipurpose satellite like its predecessors supporting the functions of communications and meteorology. The S/C structure is a cuboid of 2.0 m x 1.77 m x 2.8 m with a solar array on the south and solar sail & boom on the north (deployed length of 24.4 m).
The S/C is 3-axis stabilized using sensors, momentum and reaction wheels, solar flaps, magnetic torquers and eight 10 N and eight 22 N RCS (Reaction Control Thrusters). S/C propulsion is provided by 440 N Liquid Apogee Motor with MON-3 and Control (Mixed Oxides of Nitrogen) and MMH (Mono Methyl Hydrazine) for orbit raising. The EPS (Electric Power Subsystem) uses a solar array of 26.6 m2 providing a power of 3.1 kW. Two 70 Ah NiH2 batteries support full payload operation during eclipse periods.
The S/C design life is 12 years. The S/C launch mass is 3100kg, the S/C dry mass is 1,348 kg.
Figure 2: Photo of the INSAT-3A spacecraft during integration at Arianespace (image credit: Arianespace)
Launch: INSAT-3A was launched on Ariane 5G from Kourou on April 9, 2003. Another payload on this dual-launch was the Galaxy-12 communications satellite.
Orbit of INSAT-3A: Geostationary orbit, nominal altitude ~35,786 km, location at 93.5º east longitude.
Figure 3: Illustration of the deployed INSAT-3A spacecraft (image credit: ISRO)
Status of mission:
• The INSAT-3A spacecraft and its meteorological payload are operating nominally in 2013. 2)
• In April 2012, the INSAT-3A spacecraft is 9 years on orbit. The VHRR/2 instrument and the CCD Camera are each operated about 4 times/day. 3)
• The INSAT-3A spacecraft and its payload are operating nominally in 2011.
• The INSAT-3A spacecraft and its payload are operating nominally in 2010. 4)
• The INSAT-3A spacecraft and its payload are operating nominally in 2008. 5)
Figure 4: NDVI profile of the CCD Camera on INSAT-3A at 1 km resolution observed on Jan. 7, 2007 (image credit: ISRO)
Meteorological payload: (VHRR/2, CCD Camera, DRT, SAS&R)
The meteorological instruments are identical to those of the INSAT-2E instruments, namely VHRR/2 and the CCD Camera. A DRT (Data Relay Transponder) is flown for data collection from the ground segment. In addition, the SAS&R (Satellite Aided Search and Rescue) system is flown for COSPAS/S&RSAT rescue service provision.
VHRR/2 (Very High Resolution Radiometer):
VHRR/2 is a modified version of the VHRR heritage imagers flown on INSAT-2A, -2B, and -2E. The VHRR/2 observes in VIS, water vapor and TIR bands providing a spatial resolution of 2 km in VIS band and 8 km for the rest. VHRR/2 was developed by SAC (Satellite Application Center), Ahmedabad, India. The instrument operates in three scanning modes:
• Full frame mode (20º North-South x 20º East-West), minimum in about 33 minutes covering the entire Earth disk
• Normal frame mode (14º N-S x 20º E-W), minimum in about 23 minutes
• Sector frame mode in which the sector can be positioned anywhere in steps of 0.5º in the N-S direction to cover 4.5º N-S x 20º E-W. This mode is particularly suited for rapid, repetitive coverage during severe weather conditions like a cyclone.
The nominal frame repetition rates are: 40, 30 and 20 minutes respectively. VHRR/2 is an optomechanical system (whiskbroom type imager). The incoming solar radiation is reflected onto a Ritchey-Chretien telescope of 20 cm aperture by a beryllium scan mirror mounted at 45º to the optical axis. The optical system includes a gold-film dichoric beam-splitter that transmits visible light energy and reflects WV/TIR energy, so that the radiation from the Earth is channelized to the visible and IR focal planes simultaneously.
The visible band detector configuration consists of two staggered arrays of four silicon photodiodes each; while two sets of mercury-cadmium telluride (MCT) detector elements operating nominally at 100-110 K sense the WV/thermal radiation. The scan mirror is mounted on a two-axis, gimballed scan mechanism system to generate a 2-D image by sweeping the detector instantaneous field of view (FOV) across the Earth's surface in east to west (fast scan) and north to south (slow scan).
Table 2: Specification of the VHRR/2 instrument
Figure 5: Schematic illustration of the VHRR/2 instrument (image credit: ISRO)
Table 3: Imaging modes of the VHRR/2 instrument
Table 4: Design parameters of VHRR/2
The experimental instrument uses a linear CCD detector array with three spectral bands (see Table 5). Applications of the instrument data are in meteorology as well as in vegetation mapping. Of the three bands, the first two being similar to the NOAA AVHRR bands 1 and 2, provide “vegetation index” observation; the third band is used for snow-cover, snow-cloud discrimination and for aerosol measurements. A linear silicon array is used for the VIS and VNIR bands, while a InGaAs array is used for the SWIR band. The camera provides a nadir spatial resolution of <= 1 km in all three bands. The swath of the CCD Camera is 6300 km. The source data is coregistered and digitized to 10 bits. The data rate of the CCD Camera is 1.3 Mbit/s (QPSK modulation).
The CCD Camera was a first-time introduction on INSAT-2E. It permits greater accuracy in cyclone tracking and also affords monitoring of local severe storms. The requirements for the third-generation INSAT series call for a tandem operation, in which two members, INSAT-3A and -3D are earmarked for meteorology. While the INSAT-3A meteorological payload is still very similar to that flown on INSAT-2E (VHRR/2), the INSAT-3D payload will feature an enhanced VHRR instrument with six channels and a higher spatial resolution; two of the channels provide a split window for the TIR bands at 10.3-11.3 µm and 11.5-12.5 µm. This feature will be used to improve SST estimates.
Table 5: Specification of the CCD Camera
The CCD Camera consists of the following elements: scan mechanism assembly, optics and detector assembly, and camera electronics.
• Scan mechanism assembly: Features a gimballed scan mirror which sweeps FOV in two orthogonal axes. The fast sweep generates 300 video lines over a 6300 km east-west direction every minute (with a fast retrace capability). The 0.4º south stepping of the mirror after each east-west scan provides the generation of successive image strips. The TFOV (Total Field of View) of the mirror is ±13º in the E-W and ±10º in the N-S direction, while the actual image is ±5º in E-W and ±5º in the N-S direction. The actual image may be positioned anywhere within the mirror TFOV.
• Optics and detector assembly: The assembly consists of the scan mirror, telescope, dichroic beam splitters, fold mirror, lens doublet and bandpass filters. The front-end optics, namely scan mechanism and telescope, is identical to that of VHRR (except that the telescope performance has been upgraded to provide a FOV of ±0.25º at twice the spatial frequency of VHRR). The VIS and VNIR silicon CCD detectors have 2048 element linear arrays, as well as the InGaAs photodiode detector (cooled) for the SWIR band. The outputs of the three line arrays, providing a total of 900 pixels, are processed to construct 300 image pixels for each band.
• Camera electronics: The subsystem provides: a) clock and bias inputs to the detectors, b) processes and digitizes the detector outputs., c) formats the video signal along with auxiliary information, d) monitors the instrument; e) interfaces with other subsystems, and f) controls the SWIR detector temperature through a feedback loop.
DCS (Data Collection System):
The DRT (Data Relay Transponder) is part of a DCS (Data Collection System) of ISRO. The objective is to collect data from unattended meteorological platforms in the ground segment. DRT receives receives signals from unattended weather data collection platforms and retransmits them to the central station. The data from these payloads are being used for comprehensive weather status and forecasting.
RF communication of DRT: Uplink frequency = 402.75 MHz; downlink frequency = 4506.05 MHz; bandwidth = ± 100 kHz; EIRP = 21 dBW (min).
Note: MetSat-1 does not carry SASAR (Satellite Aided Search and Rescue) system. In the INSAT-2 series, the INSAT-2A and -2B satellites carried SASAR transponders as well as DRTs (Data Relay Transponders). According to ISRO information, INSAT-3A (launch April 9, 2003) and INSAT-3D (to be launched in late 2012), will carry SASAR and DRT payloads.
INSAT-3D is a meteorological satellite of ISRO, an exclusive mission designed for enhanced meteorological observations and monitoring of land and ocean surfaces for weather forecasting and disaster warning. The mission goals call for a significant technological improvement in sensor capabilities as compared to earlier INSAT missions. The meteorological payload features an imager and a sounder. 6) 7) 8) 9) 10)
The mission and its applications involves a technical and scientific cooperation between the following partners in India and the USA:
• Ministry of Earth Sciences(MoES) / India Meteorological Department (IMD) and
• NOAA /NESDIS (National Oceanic and Atmospheric Administration / National Environmental Satellite Data and Information Service)
NOAA/NESDIS has successfully collaborated with MoES/IMD by establishing a communication link for the exchange of INSAT satellite data & publicly available U.S. Earth observations, in operation since 1999. The establishment of the Indo-US Data Center at IMD, New Delhi has further enabled scientists to access data from India’s Kalpana & INSAT satellites as well as U.S. Earth observation data & information.
These two developments have led to a variety of scientific applications of satellite data in India & the USA. The United States wishes to expand this collaboration to include INSAT-3D Imager & Sounder data when the satellite is launched in 2011 (Ref. 9).
A MOU between NOAA and MoES was signed in 2008. In this cooperation agreement:
• NOAA/NESDIS intends to provide NOAA GOES versions of scientific algorithms and programs for operational implementation at IMD. These include source programs for rainfall estimation, sea surface temperature retrieval, vegetation index retrieval, clouds classification, cloud motion vector (visible and infra red) & water vapor winds.
• IMD will provide operational, processed, navigated/calibrated INSAT?3D data to NOAA/NESDIS through an already established dedicated communication link between IMD and NESDIS.
The INSAT-3D is a momentum-biased 3-axis stabilized spacecraft using star trackers for precise pointing control. The spacecraft has a launch mass of ~2100 kg, providing a power of ~ 1.1 kW. The nominal design life is 7.7 years.
Note: A proper spacecraft description will be provided when publications of ISRO will be available.
RF communications: Due to high data rate from theImager payload, the bandwidth requirement increases for the meteorological transmitter; a total 30 MHz bandwidth is allocated for the communication payload in INSAT-3D from 4770 - 4800 MHz in the Extended C-band. This will also provide for growth of MET payload data rate in future.
The 4500-4510 MHz downlink transmit frequency band is allocated for DRT and SAS&R transponder to maintain the present service network requirements and also to avoid interference from the spectrum roll off from the MET modulated carriers to ensure good C/I at the ground receivers for the demodulation of the carrier. The DRT will receive the signals from various DCPs (402.65 to 402.85 MHz UHF band) in random ALOHA mode. These uplink carriers are located within ±100 kHz band around the center frequency. The translated downlink frequency is at 4506.5 MHz with a bandwidth of 200 kHz. 11)
Figure 6: Illustration of the MET data modulator (image credit: ISRO)
Figure 7: Illustration of the deployed INSAT-3D spacecraft (image credit: ISRO)
Launch: A launch of INSAT-3D and of GSAT-7 (a multi-band communication satellite of ISRO) is scheduled for Q3 2013 on an Ariane-5 vehicle from Kourou, French Guiana. 12)
Orbit: Geostationary orbit, altitude ~35,786 km, spacecraft location at 82º East over the equator.
Sensor complement (Imager, Sounder, DRT, SAS&R)
Metrological payload monitors Earth’s surface and carries out oceanic observations and also provides data dissemination capabilities. It consists of:
• Six-band Imager
• Nineteen-band sounder.
The Imager is an improved design of VHRR/2 (Very High Resolution Radiometer) heritage instrument flown on the Kalpana-1 and INSAT-3A missions. The instrument features 6 spectral bands (against the 3 bands in previous versions) offering an improved 1 km resolution in the visible band for the monitoring of mesoscale phenomena and severe local storms. The two new SWIR and MWIR bands with a resolution of 1 km and 4 km, respectively, will enable better land-cloud discrimination and detection of surface features like snow. One more significant improvement is the split-band TIR channel with two separate windows in 10.2-11.2 and 11.5-12.5 µm regions with a 4 km resolution. 13)
This new element will enable the extraction of sea surface temperature over the Indian region with a far greater accuracy since the dual-window algorithm can be applied to eliminate the atmospheric attenuation effects. The 1 km resolution of the visible channel and 4 km resolution of the thermal IR channels will indirectly improve the accuracy of the derived products like outgoing longwave radiation and cloud motion vectors.
Table 6: Key parameters of the imager
The Sounder is a first time instrument of the geostationary INSAT series designed and developed at ISRO. The overall objective is to measure the temperature and humidity profiles (vertical distributions) to obtain a three-dimensional representation of the atmosphere. The instrument requirements call for soundings at 10 km ground resolution every 3 hours for a full frame scan. This enables the derivation of vertical profiles of temperature and humidity. These vertical profiles can then be used to derive various atmospheric stability indices and other parameters such as atmospheric water vapor content and total column ozone amount.
Table 7: Key parameters of the sounder
Table 8: Spectral parameters and sensitivity of the sounder
Passive radiant cooler for INSAT-3D:
A passive radiant cooler is used to cool the infrared detectors of imager and sounder instruments. The detectors temperature is maintained at 95 K (BOL) and 100 K (EOL). The passive cooler is also to maintain the sounder filter wheel temperature at 213 K. 14) 15)
DRT (Data Relay Transponder):
The DRT receives globally metrological, hydrological and oceanographic data from automatic DCPs (Data Collection Platforms) in the ground segment and relays back to downlink in Extended C -band.
Figure 8: Illustration of the DRT and the SAS&R transponders (image credit: ISRO)
SAS&R (Satellite Aided Search & Rescue):
The objective of SAS&R is to relay a distress signal / alert detection from the beacon transmitters for search and rescue purposes with global receive coverage in UHF band. The downlink will operate in Extended C-band.
2) Vinay K Dadhwal, “25 Years of Indian Remote Sensing Satellite (IRS) Series,” Proceedings of the 50th Session of Scientific & Technical Subcommittee of UNCOPUOS, Vienna, Austria, Feb. 11-22, 2013, URL: http://www.oosa.unvienna.org/pdf/pres/stsc2013/tech-44E.pdf
3) Information provided by A. S. Kiran Kumar of ISRO/SAC, Ahmedabad, India
4) V. Rajeswara Rao, A.K. Sharma , P. C. Joshi, P. K. Pal, “Current Status of INSAT Meteorological Satellites,” CGMS-38 (Coordination Group for Meteorological Satellites-38)New Delhi, India, Nov. 8-12, 2010, paper: IMD-WP-13, URL: ftp://ftp.eumetsat.int/pub/CPS/out/CGMS%2038%20report/CGMS-38%20CD/Working%20Papers%20CGMS-38/IMD/CGMS-IMD-WP-13.pdf
5) P. C. Joshi, “Indian Meteorological Satellite Missions: Current & Ülanned,” GOES-R User Conference, New Orleans, LA, USA, Jan. 23-24, 2008, URL: http://www.goes-r.gov/downloads/GOES_Users_Conference_V/GUC_V_slides/231645%20GOES-R-presentation-PCJoshi.pdf
6) Devendra Singh, “Status Report on current and future Geostationary Indian Satellites,” URL: http://cimss.ssec.wisc.edu/itwg/itsc/itsc14/presentations/session9/9_3_singh.pdf
7) V. R. Katti, V. R. Pratap, R. K. Dave, K. N. Mankad, “INSAT-3D: an advanced meteorological mission over Indian Ocean,” Proceedings of SPIE, 'GEOSS and Next-Generation Sensors and Missions,' Stephen A. Mango; Ranganath R. Navalgund; Yoshifumi Yasuoka, Editors, Vol. 6407, Goa, India, Nov. 13, 2006, DOI: 10.1117/12.697880
8) R. R. Kelkar, “Indias INSAT-3D Satellite Mission,” April 2008, URL: http://www.earthscienceindia.info/popular%20archival/download.php?file=pdf-1.pdf
10) “Implementing Arrangement Regarding INSAT-3D Satellite Data (IA-3D),” URL: http://www.star.nesdis.noaa.gov/star/documents/news/2010India/IA-3Dsignedversion.pdf
12) “Arianespace to launch GSAT 7 and INSAT 3D satellites for India,” Arianespace Press Release, Oct. 17, 2012, URL: http://www.arianespace.com/news-press-release/2012/10-17-2012-new-launch-contract.asp
13) M. R. Pandya, D. B. Shah, H. J. Trivedi, S. Panigrahy, “Simulation of at-sensor radiance over land for proposed thermal channels of Imager payload onboard INSAT-3D satellite using MODTRAN model,” Journal of Earth System Science, Vol. 120, No 1, Feb. 2011, Indian Academy of Sciences, pp. 10-25, URL: http://www.ias.ac.in/jess/feb2011/19.pdf
14) Madhu Prasad, Basavaraj S. Akkimaradi, Santram, T. Selvan, Subramanya, S. C. Rastogi, K. Badrinarayana, D. R. Bhandari, M. Sugumar, B. Mallesh, K. S. Rajam, Indira Rajgopalan, V. K. W. Grips, J. N. Balaraju, A. K. Saxena, R. Ismail Jabilullah, M. Viswanathan,Ganesh Shanbhog, “Development of Sunshield Panels for Passive Radiant Cooler On Board Meteorological Instruments of ISRO,” RASE 2009, URL: http://prints.iiap.res.in/bitstream/2248/4963/4/Development%20of%20sunshield%20panels%20for%20passive...
15) “Optical Polishing for Development of Highly Specular Sunshield for Radiant Coolers of Meteorological Satellites of ISRO,” ISRO-ISAC-TR-0908, Issue No. A, Date: 22-01-2010, URL: http://prints.iiap.res.in/bitstream/2248/5012/1/Optical%20polishing%20for%20development%20of%20highly...
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.