Joe Zender

The PROBA-V mission: image processing and calibration

With the launch of PROBA-V (Project for On-Board Autonomy – Vegetation) in 2013, the continuity and availability of global land-coverage data in four multispectral bands are ensured for the SPOT (Système Pour l’Observation de la Terre)-VEGETATION user community. This community has been served for already more than 14 years with high-quality 1 kilometre-resolution data. To guarantee continuation of this high quality over the full lifetime of PROBA-V, an operational processing platform and in-flight calibration algorithms have to be in place, which fully consider the specific PROBA-V platform and instrument design characteristics. Data quality has to be ensured for all available product levels, i.e. from the radiometrically corrected radiance data to the 10 day global synthesis. In this article we first focus on some specific design characteristics, which impose some challenges for data processing and calibration. Next, a technical description is given for all the processing steps such as mapping, cloud masking, atmospheric correction, and compositing. The functioning of the Image Quality Centre (IQC) is described. The IQC is in charge of the assessment of the PROBA-V performance, the analysis of the image quality, and the radiometric and geometric calibration after launch. Finally information is given on the distribution of the various products to the user community.

The Rosetta video approach: an overview and lessons learned so far

Purpose – Besides the technological challenge of flying a space probe for ten years before arriving at the final mission destination, one is confronted with a potential loss of knowledge during this period. The purpose of this paper is to give an overview of the general knowledge management applied for such a mission. It aims to give details for a new approach, the video approach, to capture expertise knowledge of engineers and scientists.Design/methodology/approach – The video approach included the visit of all instrument teams for several days, executing interviews with engineers, technicians and scientists. During the interviews a table of content (/toc/) with attached keywords was generated. The final video was transferred into a computer‐readable form and connected with the table of content. The methodology that was used to prepare and execute the interviews, the final video material and the storage and structure of the table of content and keywords is presented.Findings – The experimenter interviews...

Extreme Ultraviolet Solar Irradiance during the rising phase of solar cycle 24 observed by PROBA2/LYRA

The Large-Yield Radiometer (LYRA) is a radiometer that has monitored the solar irradiance at high cadence and in four pass bands since January 2010. Both the instrument and its spacecraft, PROBA2 (Project for OnBoard Autonomy), have several innovative features for space instrumentation, which makes the data reduction necessary to retrieve the long-term variations of solar irradiance more complex than for a fully optimized solar physics mission. In this paper, we describe how we compute the long-term time series of the two extreme ultraviolet irradiance channels of LYRA and compare the results with those of SDO/EVE. We find that the solar EUV irradiance has increased by a factor of 2 since the last solar minimum (between solar cycles 23 and 24), which agrees reasonably well with the EVE observations.

SMART-1 after lunar capture: First results and perspectives

SMART-1 is a technology demonstration mission for deep space solar electrical propulsion and technologies for the future. SMART-1 is Europe’s first lunar mission and will contribute to developing an international program of lunar exploration. The spacecraft was launched on 27th September 2003, as an auxiliary passenger to GTO on Ariane 5, to reach the Moon after a 15-month cruise, with lunar capture on 15th November 2004, just a week before the International Lunar Conference in Udaipur. SMART-1 carries seven experiments, including three remote sensing instruments used during the mission’s nominal six months and one year extension in lunar science orbit. These instruments will contribute to key planetary scientific questions, related to theories of lunar origin and evolution, the global and local crustal composition, the search for cold traps at the lunar poles and the mapping of potential lunar resources

PROBA-V geometric calibration

A system is described for the geometrical calibration of the planned PROBA-V multi spectral earth observation satellite. The largest challenge lies in the complex thermo-elastic distortion due to the absence of active thermal control onboard. The system is based on a 2 step (first by scene, then by global trend), weighted and constrained least squares inversion model. The geometric reference dataset consists in a set of automatically selected image chips from the Geocover 2000 dataset. Results show that the sub-pixel absolute localization accuracy requirements should be reached.

Comparing Meteor Number Fluxes from Ground-Based and Airplane-Based Video Observations

We operated identical Low-Light level TV cameras to observe the Leonid 1999 meteor storm, both from a ground-based station in Southern Spain and from the ARIA airplane of the Leonid Multi-Aircraft Campaign. The ground-based camera was pointed to a fixed position about 50° from the zenith, the airborne camera was pointed through a window at 75° from the zenith. During the peak of the Leonid storm, the two cameras were located between 10° and 20° apart in geographical longitude. The recorded meteor numbers differed by a factor 5.3 ± 0.4, the airborne camera recording the higher rates. This is much more than what could be expected from the geographical separation of the cameras. The different elevation angles and altitudes of the cameras can explain this. Pointing the camera low to the horizon results in a much larger volume in the atmosphere which is observed, resulting in higher meteor count rates. However, the meteors are on average much further away than when observing high above the horizon. The atmospheric extinction reduces the brightness of the meteors, effectively reducing the count rates. For two ground-based cameras, these two effects are expected to compensate. Due to the high altitude of the airborne camera, the increasing effect of the count rate dominates. We set up an atmospheric extinction model taking into account Rayleigh scattering that quantitatively explains the number difference. Using the same model, we predict number differences for cameras observing from the same location, but pointed at different elevation angles. For typical observing conditions, neglecting this effect can result in differences up to a factor of 10 in the derived meteor numbers.

The ESOC “Meteor Alert Center” (MALC) and Its Application during the 1999 Leonid Shower

Spacecraft operators were concerned that the high number density of meteoroid particles during the anticipated 1999 Leonid meteor storm might result in damage to spacecraft. Switching off a spacecraft is expensive and operators try to avoid it, which created a need for real time monitoring systems. At the Space Science Department of ESA, we designed a near-real time meteor monitoring system, displaying observational information at the European Space Operations Center (ESOC) in Darmstadt, Germany. The system consisted of software tools that connect automatic video systems in the field with a central data node. Here, we describe the design, implementation, setup and results of the system. Wireless communication was implemented by means of the Global System for Mobile (GSM) communication. Unfortunately, during the operational phase this communication system failed. Conventional transmission by telephone was used instead. Results of the near real time reporting are presented and discussed.