Dominique Leger

• Dr.Ing.
• Researcher at Office National d'Études et de Recherches Aérospatiales

The edge method is a widely used way to assess the on-orbit Modulation Transfer Function (MTF). Since good quality is required for the edge, the higher the spatial resolution, the better the results are. In this case, an artificial target can be built and used to ensure a good edge quality. For moderate spatial resolutions, only natural targets are...

Assessing the quality of a hyperspectral image is a difficult task. However, this assessment is required at different levels of the instrument design: evaluation of the signal to noise ratio necessary for a particular application, determining the acceptable level of losses from compression algorithms for example. It has been shown previously that a...

Hyperspectral data appear to be of a growing interest over the past few years. However, applications for hyperspectral data are still in their infancy as handling the significant size of the data presents a challenge for the user community. Efficient compression techniques are required, and lossy compression, specifically, will have a role to play,...

Hyperspectral data appears to be of a growing interest over the past few years. However, applications for hyperspectral data are still in their infancy. Handling the significant size of hyperspectral data presents a challenge for the user community. To enable efficient data compression without losing the potentiality of hyperspectral data, the noti...

Measurement of the modulation transfer function (MTF) to quantify the quality of an imaging system proves to be very important in the context of Earth observation satellites. In particular, this measurement is essential to carry out the focusing of the telescope, or to implement a deconvolution filter whose goal is to enhance the image contrast or...

In the context of Earth observation satellites such as SPOT or IKONOS, it is important to measure the modulation transfer function (MTF) and the noise in order to quantify the quality of the imaging system. This measurement is useful to decide to focus the telescope or to make a deconvolution filter whose purpose is to enhance image contrast. This...

The SPOT5 remote sensing satellite was launched in May 2002. It provides continuity of the SPOT service owing to new characteristics of its two HRG (High Resolution Geometry) cameras and its two HRS (High Resolution Stereo) cameras. The image quality performances were assessed during SPOT5's first two months of life (commissioning phase) and are st...

In the context of Earth observation satellites such as SPOT or IKONOS, it is important to measure the Modulation Transfer Function (MTF) and the noise in order to quantify the quality of the imaging system. This measurement is useful to decide to focus the telescope or to make a deconvolution filter whose purpose is to enhance image contrast. This...

The MTF (Modulation Transfer Function) is a means of characterizing the spatial resolution of the instruments. So, the MTFs of HRG and HRS cameras are parts of image quality parameters assessed during the in-flight commissioning phase. Vibrations during the launch and transition from air to vacuum may defocus the HRG cameras and degrade their MTF....

The measurement of the Modulation Transfer Function (MTF) to quantify the quality of an imaging system proves to be very important in the context of Earth observation satellites. In particular, this measurement is essential to carry out the focusing of the telescope, or to implement a deconvolution filter whose goal is to enhance the image contrast...

The measurement of the Modulation Transfer Function (MTF) to quantify the quality of an imaging system proves to be very important in the context of Earth observation satellites. In particular, this measurement is essential to carry out the focusing of the telescope, or to implement a deconvolution filter whose goal is to enhance the image contrast...

To evaluate the quality of images, most methods compare a degraded image to a perfect reference. Nevertheless in many cases, a reference does not exist. We propose an original univariant (i.e., without a reference) method based on the use of artificial neural networks. The principle behind it is to first teach a neural network to assess image quali...

The signal to noise ratio is one of parameters checked in flight to assess the image quality of remote sensing satellites. A simple method to estimate this parameter consists in selecting huge snowy areas. As the landscape is nearly uniform, a correct estimation of the standard deviation of the noise can be done by calculating the standard deviatio...

In order to evaluate the visual quality of images, most methods compare a degraded image to a perfect reference. We propose an original univariant (i.e. without reference) method based on the use of artificial neural networks. The principle is first to use a neural network to learn the quality of images taken from a pool of known examples, then use...

The SPOT4 remote sensing satellite was successfully launched at the end of March 1998. It was designed first of all to guarantee continuity of SPOT services beyond the year 2000 but also to improve the mission. Its two cameras are now called HRVIR since a short-wave infrared (SWIR) spectral band has been added. Like their predecessor HRV cameras, t...

A successful in-flight refocusing experiment based on image processing is described. Each of the two SPOT1 HRV cameras was refocused with respect to the other by analyzing the image spectrum taken simultaneously by both cameras. The experiment was carried out during the autumn of 1994 and its results are also presented: (1) the estimated optimal po...

For Earth observation satellites such as SPOT, it is important to measure the modulation transfer function (MTF) in order to quantify the spatial resolution of the imaging system. This measurement is useful to decide to focus the telescope or to make a deconvolution filter whose purpose is to enhance image contrast by ground processing. The paper p...

First Page of the Article

Time of flight anemometry techniques have been added to a coherent CO2 laser Doppler anemometer for performing simultaneous measurements of radial and transverse wind velocity components.

The modulation transfer function (MTF) was assessed, in the panchromatic mode, using a visual comparison between SPOT images and images from a reference catalog, made using aerial high resolution photographs over cities. The photographs were digitized, deteriorated by application of known MTF, and put in SPOT format. The comparison indicates that t...

The SPOT MTF is tested during the post-launch performance assessment using a photointerpretative method. To this end an image catalog is prepared before launch. This catalog is based on aerial high resolution photographs of 20 cities in the Southern part of France in the panchromatic band. Each photograph is subsequently digitized and sampled at a...

In a previous article we have shown that the two speckle patterns produced from the same rough surface illuminated by two coherent plane waves under two different angles of incidence are correlated. The correlation depends on the surface roughness. In this paper a method is described where the rough surface is illuminated simultaneously by the two...

Two speckle patterns produced from the same rough surface by two different illuminations are correlated. The correlation depends on the surface roughness. The two illuminations were obtained here by varying the angle of incidence of a coherent plane wave on the surface. The speckle patterns are recorded on the same film by double exposure. By placi...

- La qualité des images des caméras satellitaires est régulièrement contrôlée en vol. La fonction de transfert de modulation (FTM) est un des critères de qualité image. Sa connaissance permet d'estimer ou de comparer les performances en vol de différents satellites et est utile pour calculer des filtres de déconvolution. Nous proposons une méthode...