Minimize EgyptSat-1

EgyptSat-1

EgyptSat-1 (also referred to as Misrsat-1) is an international collaborative minisatellite project of NARSS (National Authority for Remote Sensing and Space Science) of Egypt and the Yuzhnoye State Design Office (YSDO), Dnepropetrosvk, Ukraine. In 2001, Yuzhnoye won the contract to design and develop the satellite, providing also technical expertise and on-the-job training to 60 Egyptian engineers and experts as well as technology transfer.

The industrial consortium consisted of Ukrainian companies with Yuzhnoye as as prime contractor responsible for the platform and the launch. SSRE “CONECS” was responsible for the development of the two optical payloads, the onboard payload command and data handling subsystem, as well as for the development of the data processing in the ground segment. Subcontractors to SSRE CONECS were “Arsenal” in Kiev for optics manufacturing, SRDI “Elvit” for the onboard data processing and XenICs nv for the SWIR array manufacturing. 1)

EgyptSat-1 is the first remote sensing satellite of Egypt funded by the government of Egypt. The objective is to fly two instruments: a multispectral imager and an infrared imager. 2) 3) 4) 5)

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Figure 1: Artist's rendition of the deployed EgyptSat-1 spacecraft (image credit: NARSS)

Spacecraft:

The spacecraft design features a modular bus (frame-type modules). The spacecraft has a launch mass of 165 kg (minisatellite). The design life is 3 years with a goal of 5 years. The EgyptSat-1 spacecraft was developed by the Yuzhnoye State Design Office and produced by the State Enterprise Production Association Yuzhny Machine-Building Plant.

Unfortunately, a description of the spacecraft and its subsystems (published paper) was not available from NARSS.

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Figure 2: General layout of the deployed EgyptSat-1 spacecraft without side panels (image credit: NARSS)

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Figure 3: Block diagram of the EgyptSat-1 spacecraft (image credit: NARSS)

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Figure 4: EgyptSat -1 under assembly in the nose cone of the Dnepr launcher along with other payloads (image credit: NARSS)

Launch: EgyptSat-1 (primary payload) was launched on April 17, 2007 on a Dnepr-1 launch vehicle from the Cosmodrome in Baikonur, Kazakhstan. Launch provider: ISC (International Space Company) Kosmotras of Moscow, Russia.

Secondary payloads on this multi-spacecraft launch were: SaudiSat-3 (35 kg), SaudiComsat-3 (12 kg), SaudiComsat-4 (12 kg), SaudiComsat-5 (12 kg), SaudiComsat-6 (12 kg), SaudiComsat-7 (12 kg), AKS-1 (12 kg), AKS-2 (12 kg), and 7 CubeSats: PolySat-4 (1 kg, CalPoly), CAPE-1 (1 kg, University of Louisiana), PolySat-5 (1 kg), Libertad-1 (1 kg, University of Sergio Arboleda, Columbia), AeroCube-2 (1 kg, The Aerospace Corporation, El Segundo, CA), CSTB-1 (1 kg,CubeSat TestBed-1, Boeing Company), and MAST [3 kg, Multi-Application Survivable Tether, Stanford University, TUI (Tethers Unlimeted)]. 6)

The CubeSats were deployed after the primary spacecraft was deployed into a nearly circular polar orbit. Three P-PODs contained the 6 single CubeSats and 1 triple CubeSat for MAST.

Orbit: Sun-synchronous orbit, altitude = 668 km, inclination = 98.1º, period = 98.1 minutes. The local equator crossing time is at 10:30 hours, the revisiting time is ~ 13 days after 191 orbital periods.

RF communications: The S-band is used for TT&C support. The X-band is used to downlink the payload data (imagery). An on-board memory system stores the payload data when not in contact with a station.


 

Mission status:

• In July 2010, NARSS lost communications and control of the EgyptSat-1 spacecraft. All attempts by NARSS and by Yuzhnoye to regain control of the spacecraft failed so far. NARSS reported this event on October 23, 2010. After 3 years of on orbit operations, the mission of EgyptSat-1 can be regarded as ended.

• The spacecraft and its payload are operating nominally in 2010. 7)

• The spacecraft and its payload are operating nominally in 2008. 8)

• On April 10, 2008, the Egyptian ground control station for EgyptSat-1 was inaugurated.


 

Sensor complement: (MBEI, IREI)

Both instruments were designed and developed at SSRE CONECS in Lviv, Ukraine. This included also the PLCDHS (PayLoad Command and Data Handling System) for on-board data handling, data storage, compression and data transfer to the X-band communication system (Ref. 1). 9)

MBEI (MultiBand Earth Imager):

MBEI is a Pan (panchromatic) and MS (Multispectral) pushbroom imager providing co-registered imagery of the target area in Pan and 3 narrow MS bands within the VNIR (Visible Near-Infrared) spectral region. Some the the spectral bands are identical with those of the Vegetation instrument on SPOT missions.

The compact instrument has a mass of only 26 kg. The power dissipation of the sensors and associated driving and buffering electronics is limited to 25 W. The unit is also equipped with an additional heater of 25 W to stabilize the temperature of the instrument.

The overall objective of the MBEI instrument is to observe the irradiance coming from the soil and the vegetation. The first band (B1) is being used to make atmospheric corrections; the panchromatic channel is present to enhance the situational awareness and to ease the interpretation of the acquired data (Ref. 1).

Instrument type

Pushbroom imager

Number of spectral bands

4

Spectral bands

B1: 0.50 - 0.59 µm
B2: 0.61 - 0.68 µm
B3: 0.79 - 0.89 µm
B4: 0.50 - 0.89 µm (panchromatic)

Spatial resolution

7.8 m at nadir

Swath width, FOV (Field of View)

46.6 km at nadir, 4º

Spacecraft body pointing capability

±35º (repointing is provided by spacecraft rotation)

FOR (Field of Regard)

980 km

Optics:
Focal length
Diameter of entrance pupil
Lens aperture


860 nm (folded optics)
170 mm
1:5 (f/5)

SNR (Signal-to-Noise Ratio)

> 150 for MS bands, > 300 for panchromatic band

MTF (modulation Transfer Function)

25% (B1), 20% (B2), 15% (B3), 18% (B4)

Detector line array

4 linear CCD arrays with 6000 pixels each (CCD191 from Fairchild Imaging Inc.)

Source data rate per band

46.08 Mbit/s (the total data rate to mass memory is ~ 184 Mbit/s)

Instrument power consumption

< 50 W (without heating), < 25 W (with heating)

Instrument mass

26 kg

Table 1: Performance parameters of the MBEI instrument

IREI (Infrared Earth Imager):

The objective of IREI is to observe the irradiance form the target area in one SWIR (Short Wavelength Infrared) spectral band. The instrument features one optically butted module, consisting of 3 linear arrays with 500 InGaAs pixels each (Ref. 1).

This instrument is aligned with the MBEI instrument and is operated at 4 times the pitch of the VNIR bands. Due to the increased pitch, the optics is twice as small; the power of the IREI instrument is also lower than that of the higher speed MBEI instrument.

Instrument type

Pushbroom imager

Spectral band

1.55 - 1.7 µm

Spatial resolution at nadir

39 m (cross-track) x 46 m (along-track)

Swath width at nadir

55 km

Spacecraft body pointing capability

±35º (repointing is provided by spacecraft rotation)

FOR (Field of Regard)

980 km

Optics:
Focal length
Diameter of entrance pupil
Lens aperture


430 mm
97 mm
f/4.4

SNR

> 100 (at max. illuminance)

MTF

35%

Detector line array

3 linear arrays with 500 InGaAs pixels each. The detector has a spectral range of 1.1-1.7 µm but IREI has spectral band 1.55 - 1.7 µm due to the optical filter

Source data rate

1.92 Mbit/s

Instrument power consumption

18 W (without heating), < 25 W (with heating)

Instrument mass

14 kg

Table 2: Performance parameters of the IREI instrument

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Figure 5: IREI instrument in its test frame at the CONECS test bench (image credit: SSRE CONECS)

FPA (Focal Plane Assembly): The FPA of the IREI features a fourfold lower spatial resolution than the imagery of the MBEI instrument. Three linear line InGaAs arrays, consisting of a central PDA (PhotoDiode Array) with 500 pixels, and 2 ROIC (Readout Integrated Circuit) modules are optically butted around a central beam splitter. In this way the needed space is created to accommodate the packaged sensor arrays. To allow the reordering of the pixels in ground processing, there is an overlap of 25 pixels in the butting edge.

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Figure 6: Schematic view of the optically butted InGaAs SWIR FPA arrangement (image credit: SSRE CONECS)

The detector arrays are mounted in a modified metal can package. As the instrument ambient is kept constant between 15-25ºC, it is not necessary to introduce a thermoelectric or a Peltier cooler in the package. This measure allowed to reduce the wall height of the package and also the size of the fixation flanges.

The PDA of 500 effective pixels on a pitch of 25 µm is mounted in a metal can which is wire-bonded to 2 CMOS ROICs (with 256 inputs each on a pitch of 50 µm). For the interconnection of the PDA to the ROIC’s a double wire bonding layer on a pitch of 100 µm is used. The PDA and the 2 ROICs are placed on a alumina substrate together with 4 resistors, 4 capacitors and 5 kΩ @ 25ºC NTC.

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Figure 7: Photo of an uncapped linear array assembly with a central PDA, 2 ROICs and auxiliary passive components (image credit: SSRE CONECS)

PLCDHS (PayLoad Command and Data Handling System):

The MBEI and IREI source data, preconditioned by the proximity electronics, are further treated and stored by the PLCDHS. This system is capable of treating a data stream of 48 Mbit/s; it has a storage capacity of 2 GByte. Prior to transmission to the ground station, the data are compressed, combined with telemetry data and formatted. Then the data are sent to the X-band communication unit of the platform.

MBEI source data rate (four bands)
IREI source data rate

~184 Mbit/s
1.92 Mbit/s

Mass memory capacity

2 GByte

Data compression rate range

1.5 - 4

Data output rate to X-band transmitter

30.72 Mbit/s (after application of compression algorithm)

Peak power consumption

< 35 W

Instrument mass, volume

< 7 kg, < 6800 cm3

Table 3: Summary of the PLCDHS instrument parameters

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Figure 8: MBEI image of Cairo city center (image credit: NARSS)


1) Oleg Lapshinov, Viktor Tkachenko, Leonid Varichenko, Jan Vermeiren, “Design, Development and First Assessment of the SWIR Instrument for Remote Sensing on Board of EgyptSat-1,” Proceedings of the IAA Symposium on Small Satellite Systems and Services (4S), Rhodes, Greece, May 26-30, 2008, ESA SP-660, August 2008

2) http://www.nkau.gov.ua/nsau/catalogNEW.nsf/...

3) S. W. Samwel, A. A. Hady, J. S. Mikhail, Y. S. Hanna, Makram Ibrahim, “Analysis of the space radiation environment of EgyptSat-1 satellite,” IAGA (International Association of Geomagnetism and Aeronomy) International Symposium: Space Weather and its Effects on Spacecraft, p: 40, October 5-9, 2008, Cairo, Egypt.

4) Stanislav Konyukhov, “Satellite for Egypt from the Dnepr River Bank,” Yuzhnoye, Oct. 11, 2007, URL: http://www.yuzhnoye.com/?idD=80&lang=en&id=20&path=Digests/Digests_e

5) Hamdy A. Ashour, “The Egyptian Space Program & its Role in the Sustainable Peaceful Development of Egypt, Middle East & Africa,” URL: http://www.oosa.unvienna.org/pdf/sap/2007/morocco/presentations/6-5.pdf

6) http://www.russianspaceweb.com/dnepr_008_egyptsat1.html

7) Information provided by A. M. Elhady of NARSS, Kairo, Egypt

8) M. Mahmoud, A. Mahmoud, M. El-Sirafy, A. Hassan, A. Farrag, A. Zaki, “Microsatellites commissioning hands on experience,” Proceedings of the International Workshop on Small Satellites, 'New Missions, and New Technologies,' SSW2008, Istanbul, Turkey, June 5-7, 2008

9) Zahraa Mohamed Abd Al-Rahman, “Assessment Of Egyptian Satellite (EGYPTSAT-1) Images For The Production and Updating Of 1:25000 Planimetric Maps,” URL: http://www.aag.org/galleries/gisum_files/AlRahman.pdf


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.