RADARSAT-1/RADARSAT-2/ENVISATRADARSAT-1/RADARSAT-2/ENVISATMission StatusMission Status

Adrian BohaneAdrian Bohane

IICWGIICWGSt. Petersburg April 2003St. Petersburg April 2003

RADARSAT-1 MissionRADARSAT-1 Mission

RADARSAT Mission Life was specified for 5.25 years from launch in November 1995.

The 5.25 year goal was a program requirement from the Canadian government; the satellite and ground infrastructure were built in response to this and to meet or exceed the program goal. Significant redundancy was built into all aspects of the program.

The satellite is working well and is producing reliable and good quality data going into the 8th year of operation

Momentum Wheels: December outageMomentum Wheels: December outage

RADARSAT has 2 sets of 3 orthogonal wheels that measure changes in the spacecraft inertia and provide input to the attitude correction system

During fall of 1999, speed variations were observed in 1 wheel of the primary set possibly due to breakdown or loss of lubricant.

In October 1999 all wheels were switched from primary to redundant; the ‘all wheel switch’ was the only one configured at CSA; redundant wheels continue to perform well. Procedures have been developed subsequently to switch individual wheels

Momentum Wheels (cont’d)Momentum Wheels (cont’d)

In the fall of 2002, the primary pitch wheel was restarted to test its performance; no improvement was observed

Shortly after, the redundant pitch wheel displayed similar indications of high temperature and speed variation; it was shut down in December 2002

Over a 4 week period in December 2002 procedures were developed and simulated to operate the spacecraft without input from the pitch momentum wheel; this procedure uses the torque rods to provide input in place of the wheel and one of the pitch wheels is kept stationary and used as a reaction wheel

Operations resumed on 24 December 2002; subsequent analysis has shown that the satellite pointing and stability are as good as they were prior to shutdown of the pitch wheel

Horizon Scanner Horizon Scanner

HS2 failed in first year of operations; cause is not yet clear

HS1 has been used successfully, but since April 2000 warnings regarding motor speed control have been received in telemetry perhaps indicating impending bearing failure

If both fail risk: management has focused upon improving spacecraft performance using Attitude Determination Method 3 (ADM3) and on reduction of risks during critical attitude control regimes (Eclipse entry/exit transitions)

Tests conducted to date show that spacecraft can be controlled in ADM3 mode sufficiently well to permit successful imaging ; ground processors have been validated for handling the data

Failure of both HS1 and HS2 would therefore not end the mission because of redundant sources of attitude information

Consumables Consumables

Main consumable is propellant required to maintain orbit

Currently, burns are more frequent than at first due to solar pressure effects during solar maximum; Solar maximum peaked in summer 2000 and has been declining since

Change to orbit maintenance strategy (+/- 2 km) has no impact on total fuel consumption

It has been estimated that sufficient fuel remains to maintain orbit beyond 2070

Spacecraft Power Spacecraft Power

Ability of the solar array (SA) to generate power degrades with time; Original estimate was that SA power would last for 2-3 years beyond nominal life; On-going monitoring of degradation indicates 2012 to be a more realistic date

Therefore no threat to mission expected for several years

On Board Tape Recorders (OBR)On Board Tape Recorders (OBR) RADARSAT-1 has 2 mechanical on board recorders, both performed

well until April 2002.

In late April 2002, OBR 1 showed sudden signs of high error, preliminary analysis indicated a failure and it was shut down; Recently OBR 1 was restarted and successfully used to record data.

OBR 2 continues to work well but in order to conserve the tape recorder life the number of playbacks per day was reduced from 3 or 4 to 1.

Bit Error Rate analysis of both recorders is constantly monitored.

Leonids Leonids

In 1999 predictions prompted shutdown of the payload high-voltage units for 12 hours on 18 November to prevent arcing

2000 event was insignificant

2001 event was predicted to be 5x greater than 1999; similar high-voltage shutdown strategy employed as in 1999

Predictions are monitored each year and risk mitigation strategy employed as necessary

Summary of Satellite HealthSummary of Satellite Health

Sudden catastrophic failure is always a risk

There is no key component currently indicating that is likely to fail or expire prior to the scheduled launch of RADARSAT-2

Strategies and ‘work-arounds’ exist and are development is on-going to extend the mission

RSI is optimistic that RADARSAT-1 will remain operational until the launch of RADARSAT-2

RADARSAT-2 StatusRADARSAT-2 Status

RADARSAT-2 is currently in the manufacturing phase and is scheduled for launch in 2005. A Boeing Delta launch is the chosen vehicle.– Launch is dependent on the end of the manufacturing phase. The

main complex component is the active antenna and the 512 tx/rx modules on the antenna. The end of the production run of the modules (known in 6 months) is the key determinant in the launch date.

– The current manufacturing schedule points to a launch in early to late 2005.

First pre-launch commitment signed recently between Norwegian and Canadian governments and respective commercial partners (RSI and KSAT).

ENVISAT UpdateENVISAT Update

Adrian BohaneAdrian Bohane

IICWGIICWGSt. Petersburg April 2003St. Petersburg April 2003

ENVISAT InstrumentsENVISAT Instruments

MERIS - Medium Resolution Imaging Spectrometer

MIPAS - Michelson Interferometric Passive Atmospheric Sounder

GOMOS - Global Ozone Monitoring by Occultation of Stars

RA2 - Radar Altimeter 2

MWR - Microwave Radiometer

LRR - Laser Retro Reflector

ASAR - Advanced Synthetic Aperture Radar

ENVISAT Image AcquisitionENVISAT Image Acquisition Modes Modes

ESA Multi-instrument with C-band ASAR on board

Launched March 2002

Operational 2003? (Officially 1st May 2003)

Image mode (100km x 100km, 30m resolution)

Wide Mode (400km x 400km, 150m resolution)

ENVISAT ImagingENVISAT Imagingand Viewing Anglesand Viewing Angles

Image

Wide Swath

Alternating/Cross Polarisation

Wave

Global Monitoring

100

400

100

5

400

30

150

30

10

1000

Nominal Swath Width (km)

Nominal Resolution

(m)

Polarisation

VV or HH

VV or HH

VV/HH, VV/VH or HH/HV

VV or HH

VV or HH

ENVISAT Mission ScenariiENVISAT Mission Scenarii

Primary downlink to ESA X-Band stations at Kiruna (Sweden) and Matera (Italy). Production at processing and archive centres (PAC) in UK, Germany and Italy (ESRIN).

Other direct X-Band downlink planned when requested by authorised National or Foreign Ground Stations e.g. Canada (Gatineau and Prince Albert), Norway (Tromsø and Svalbard).

SSR data downlinked to Kiruna and Svalbard. Data can also be relayed via Artemis relay satellite (first successful test 2 weeks ago)

Data DistributionData Distribution

Category 1 - Academic/Research and Application Development (Announcement of Opportunity - AO)

Category 2 - Operational/Commercial Use

Category 2 requests have priority over Category 1 in ASAR tasking

Category 2 users must purchase data through a Distributing Entity (DE): SARCOM, EMMA

Data DistributionData Distribution

SARCOM Consortium

Distributing Data from ERS and Envisat Worldwide

Aimed at supporting a sales strategy for providing multi-source satellite imagery

SARCOM Members include– RADARSAT International– Kongsberg (KSAT)

Data AvailabilityData Availability Official date: May 1st, 2003

Order tracking?

Priority Programming?

NRT Processing?

Guarantee of Image Acquisition?

The above still needs to be clarified with ESA and will become clearer over the coming weeks

KSAT currently ready for NRT services

RSI/CDPF ready for NRT June 2003