Envisat

 2002-009A

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ESA's Polar Platform, Envisat, was originally conceived as an automated polar orbit counterpart to the Space Station. The Polar Platform was split into Envisat and MetOp. 

By 1996 the program had been downsized to a single huge satellite for launch on Ariane 5, with a mass of 8211 kg (8111 kg?) including 2050 kg of payload and 314 kg of hydrazine, a width of 4.5 m and a length of 10.5m. On orbit it is 26m x 10m x 4.5m. The SVM (service module) holds the AOCS and the solar array. The PLM (Payload module) consists of the PLC (formerly PPF Polar Platform) payload carrier on one side and the PEB on the other side. The prime contract was given to Daimler-Benz Aerospace's Dornier Satellitensysteme GmbH (later Astrium) subsidiary. The Polar Platform satellite bus was built by Matra Marconi Space's Bristol plant; after Bristol was closed, final integration was done at ESTEC. The bus design can take up to 5 segments, with Envisat 1 using 4 plus a SPOT 4 class service module and a solar array.

The C-band ASAR is 1.3 x 10m in size. It features an active phased array antenna, in contrast to the passive radiator array on ERS-1 and ERS-2. In image mode it has a 100 km swath with 30m resolution. MERIS is a visible/near-IR (3900A-1.0 micron) spectrometer with a 1150 km swath, and will be used for ocean pigment and plankton studies, cloud and vegetation observations. The AATSR is a follow on to the ATSR on the ERS satellites and measures sea surface temperature and land vegetation. with a 1 km resolution. It has visible and IR (1.6 to 12 micron) channels. GOMOS determines atmospheric constituents from their changing absorption in the spectra of stars mag 2 and brighter near the horizon as a function of airmass. MIPAS gets emission lines from the horizon in the mid IR to monitor trace gases. SCHIAMACHY measures trace gaces by optical spectra at the nadir and on the horizon. The RA-2 is another ERS follow-on, and uses 13.6 and 3.2 GHz signals for radar altimetry. A microwave radiometer (MWR) is used to provide path length corrections due to atmospheric humidity. DORIS is a Doppler receiver which uses ground signals to measure its orbit, the inverse of the Transit navigation scheme which used a satellite radio beacon and ground receivers.

Envisat will use the Ariane 5 Long Fairing. The satellite will be placed in an 800 km sun synch. orbit with a 35-day repeat cycle and a 10:00 descending node mean local solar time. It has an X-band downlink to Kiruna and an intersatellite link to Artemis. Flight control is at ESOC with commanding from Kiruna and Svalbard.

In 2010 Jun a mission extension was approved with a 2010 Oct orbit change from 800 km to 782 km using 33 kg of prop. Contact with the satellite was lost in 2012 Apr.

V145 was the first use of the 17m Long Fairing. EPS dry mass is 1200 kg.

Launch 749t 50.4m high. Launch to north.

Envisat
Date	Time	Event	Orbit
2002 Mar 1		T-0:07 EPC MES
	0107:59	Launch by Ariane 5G V145 (511)	CSG ELA2
		T+2:18 EAP sep
		T+3:07 Fairing sep
		T+9:48 EPC MECO
	0117	T+9:54 EPC sep at 347 km	-2610 x 651 x 98.5
	0118:00	T+10:01 EPS MES
	0125	EPC apogee 651 km
	0130	T+23:30?	0 x 791
	0133	T+25:16 EPS MECO
	0134	T+26:51 EPS sep	100.36 766 x 784 x 98.5
	0136	EPC impact Canadian Arctic 82.9N 107W
2002 Apr 1			100.61 784 x 790 x 98.6
2002 Apr 5		Op orbit reached	100.54 783 x 784 x 98.5
2002 Apr 10			100.54 783 x 784 x 98.5
2010 Oct 22			100.54 783 x 784 x 98.5
2010 Oct 22		Orbit adjust	100.34 773 x 775 x 98.5
2010 Oct 26		Orbit adjust	100.18 765 x 768 x 98.5
2011 Jan 15			100.18 766 x 767 x 98.5
2012 Apr 8		end of ops	100.18 766 x 767 x 98.5

Payload:

• SVM Service Module (MMS-Toulouse)

• PEB Payload Equipment Bay (Dornier)

  • Ka-band intersatellite link

• PPF Payload carrier (Polar Platform) (MMS-Bristol)

  • MERIS Medium res imaging spectrometer (ESA) 3900A-1 Mu.

  • MIPAS Michelson interferometer for passive atmospheric sounding (ESA) 4-14.6Mu

  • ASAR Advanced SAR (ESA) 1.3 x 10m antenna

  • GOMOS Global Ozone monitoring by occultation of stars (ESA) UV/vis/NIR spectrometer

  • RA-2 Adv radar Altimeter (ESA) 13.6 and 3.2 GHz.

  • MWR Microwave radiometer(ESA) Dicke radiometer at 23.8 and 36.5 GHz.

  • LRR Laser Retro-Reflector (ESA)

  • AATSR (UK) Advanced along track scanning radiometer, 6700A-12 Mu.

  • SCIAMACHY Scanning imaging absorption spectrometer for atmospheric cartography, 2400A-2.4Mu