Achievable debris orbit prediction accuracy using laser ranging data from a single station

Earlier studies have shown that an orbit prediction accuracy of 20 arc sec ground station pointing error for 1–2 day predictions was achievable for low Earth orbit (LEO) debris using two passes of debris laser ranging (DLR) data from a single station, separated by about 24 h. The accuracy was determined by comparing the predicted orbits with subsequent tracking data from the same station. This accuracy statement might be over-optimistic for other parts of orbit far away from the station. This paper presents the achievable orbit prediction accuracy using satellite laser ranging (SLR) data of Starlette and Larets under a similar data scenario as that of DLR. The SLR data is corrupted with random errors of 1 m standard deviation so that its accuracy is similar to that of DLR data. The accurate ILRS Consolidated Prediction Format orbits are used as reference to compute the orbit prediction errors. The study demonstrates that accuracy of 20 arc sec for 1–2 day predictions is achievable.     

Improved kHz-SLR tracking techniques and orbit quality analysis for LEO missions

Satellite gravity field missions such as CHAMP, GRACE and GOCE are designed as low Earth orbiting spacecraft (LEO) with orbit heights of about 250–500 km. The challenging mission objectives require a very precise knowledge of the satellite orbit position in space. For these missions precise orbit information is typically provided by GPS satellite-to-satellite tracking (SST) observations supported by satellite laser ranging (SLR).     

Accurate orbit predictions for debris orbit manoeuvre using ground-based lasers

Orbit manoeuvre of low Earth orbiting (LEO) debris using ground-based lasers has been proposed as a cost-effective means to avoid debris collisions. This requires the orbit of the debris object to be determined and predicted accurately so that the laser beam can be locked on the debris without the loss of valuable laser operation time. This paper presents the method and results of a short-term accurate LEO (<900 km in altitude) debris orbit prediction study using sparse laser ranging data collected by the EOS Space Debris Tracking System (SDTS). A main development is the estimation of the ballistic coefficients of the LEO objects from their archived long-term two line elements (TLE). When an object is laser tracked for two passes over about 24 h, orbit prediction (OP) accuracy of 10–20 arc seconds for the next 24–48 h can be achieved – the accuracy required for laser debris manoeuvre. The improvements in debris OP accuracy are significant in other applications such as debris conjunction analyses and the realisation of daytime debris laser tracking.     

Spin axis orientation of Ajisai determined from Graz 2 kHz SLR data

The Graz 2 kHz Satellite Laser Ranging (SLR) measurements allow determination of the spin axis orientation of the geodetic satellite Ajisai. The high repetition rate of the laser makes it possible to determine the epoch time when the laser is pointing directly between two corner cube reflector (CCR) rings of the satellite. Identification of many such events during a few (up to 3) consecutive passes allows to state the satellite orientation in the celestial coordinate system. Six years of 2 kHz SLR data (October 2003–October 2009) delivered 331 orientation values which clearly show precession of the axis along a cone centered at 14^h56^m2.8^s in right ascension and 88.512° in declination (J2000.0 celestial reference frame) and with an half-aperture angle θ of 1.405°. The spin axis precesses with a period of 117 days, which is equal to the period of the right ascension of the ascending node of Ajisai’s orbit. We present a model of the axis precession which allows prediction of the satellite orientation – necessary for the envisaged laser time transfer via Ajisai mirrors.     

Time Transfer by Laser Link: Data analysis and validation to the ps level

The Time Transfer by Laser Link (T2L2) is a very high resolution time transfer technique based on the recording of arrival times of laser pulses at the satellite. T2L2 was designed to achieve time stability in the range of 1 ps over 1000 s and an accuracy better than 100 ps. The project is in operation onboard the Jason-2 satellite since June 2008. The principle is based on the Satellite Laser Ranging (SLR) technology; it uses the input of 20–25 SLR stations of the international laser network which participate in the tracking. This paper focuses on the data reduction process which was developed specifically to transform the raw information given by both space instrument and ground network: first to identify the triplets (ground and onboard epochs and time of flight of the laser pulse), second to estimate a usable product in terms of ground-to-space time transfer (including instrumental corrections), and thirdly to produce synchronization between any pair of remote ground clocks. In describing the validation of time synchronizations, the paper opens a way for monitoring the time difference between ultra-stable clocks thanks to a laser link at a few ps level for Common View passes. It highlights however that without accurately characterizing the onboard oscillator of Jason-2 and knowing the unavailability of time calibrations of SLR stations generally, time transfer over intercontinental distances remain difficult to be accurately estimated.     

Spin rate and spin axis orientation of LARES spectrally determined from Satellite Laser Ranging data

Satellite Laser Ranging (SLR) is a powerful technique able to measure spin rate and spin axis orientation of the fully passive, geodetic satellites. This work presents results of the spin determination of LARES – a new satellite for testing General Relativity. 529 SLR passes measured between February 17 and June 9, 2012, were spectrally analyzed. Our results indicate that the initial spin frequency of LARES is f₀ = 86.906 mHz (RMS = 0.539 mHz). A new method for spin axis determination, developed for this analysis, gives orientation of the axis at RA = 12^h22^m48^s (RMS = 49^m), Dec = −70.4° (RMS = 5.2°) (J2000.0 celestial reference frame), and the clockwise (CW) spin direction. The half-life period of the satellite’s spin is 214.924 days and indicates fast slowing down of the spacecraft.     

Impact effects from small size meteoroids and space debris

When the impact risk from meteoroids and orbital debris is assessed the main concern is usually structural damage. With their high impact velocities of typically 10–20 km/s millimeter or centimeter sized objects can puncture pressure vessels and other walls or lead to destruction of complete subsystems or even whole spacecraft. Fortunately chances of collisions with such larger objects are small (at least at present). However, particles in the size range 1–100 μm are far more abundant than larger objects and every orbiting spacecraft will encounter them with certainty. Every solar cell (8 cm² area) of the Hubble Space Telescope encountered on average 12 impacts during its 8.25 years of space exposure. Most were from micron sized particles.     

Observation of the lunar topography by the laser altimeter LALT on board Japanese lunar explorer SELENE

The SELENE Laser Altimeter (LALT) is designed to map the Moon’s topography and will be launched in summer 2007. LALT incorporates Q-switched Cr doped Nd:YAG laser (1064 nm) with an output energy of 100 mJ and 1 Hz repetition frequency for about one year mission period. The laser pulse travels to the Moon’s surface and reflections from the surface are detected by a silicon avalanche photo-diode. The ranging distance is 50–150 km with about 5 m accuracy. Several corrections for accurate ranging data are investigated. The flight hardware has been qualified and passed all the integration tests. A principal goal of the LALT instrument is to obtain a much more detailed lunar topographic map which is superior in global coverage, measurement accuracy and number of data points to previous observations and models. The overall science objectives of LALT are (1) determination of lunar global figure, (2) internal structure and surface processes, (3) exploration of the lunar pole regions, and (4) reduction of lunar occultation data.     

Contribution of satellite laser ranging to combined gravity field models

In the framework of satellite-only gravity field modeling, satellite laser ranging (SLR) data is typically exploited to recover long-wavelength features. This contribution provides a detailed discussion of the SLR component of GOCO02S, the latest release of combined models within the GOCO series. Over a period of five years (January 2006 to December 2010), observations to LAGEOS-1, LAGEOS-2, Ajisai, Stella, and Starlette were analyzed. We conducted a series of closed-loop simulations and found that estimating monthly sets of spherical harmonic coefficients beyond degree five leads to exceedingly ill-posed normal equation systems. Therefore, we adopted degree five as the spectral resolution for real data analysis. We compared our monthly coefficient estimates of degree two with SLR and Gravity Recovery and Climate Experiment (GRACE) time series provided by the Center for Space Research (CSR) at Austin, Texas. Significant deviations in C₂₀ were noted between SLR and GRACE; the agreement is better for the non-zonal coefficients. Fitting sinusoids together with a linear trend to our C₂₀ time series yielded a rate of (−1.75 ± 0.6) × 10⁻¹¹/yr; this drift is equivalent to a geoid change from pole to equator of 0.35 ± 0.12 mm/yr or an apparent Greenland mass loss of 178.5 ± 61.2 km³/yr. The mean of all monthly solutions, averaged over the five-year period, served as input for the satellite-only model GOCO02S. The contribution of SLR to the combined gravity field model is highest for C₂₀, and hence is essential for the determination of the Earth’s oblateness.     

Height and time variability of planetary wave activity

The height–season and year-to-year regularities of parameters of first and second spatial harmonics determine the structure of the stratosphere and mesosphere circulation and its variability. In the period 1992–2002 at heights 0–55 km, the amplitudes and phases of the first and second spatial harmonics in the field of temperature, geopotential height, zonal and meridional wind were calculated by the method of harmonic decomposition. Dispersion (standard or mean square deviation) of their day-to-day and year-to-year variations was calculated by their wavelength constants. Height and season patterns of variability have been estimated. The difference in height–longitude variability for wave numbers m = 1 and 2 has been discovered. At the same time, the intensity of wave disturbances for m = 1 is less than for m = 2 excluding the polar areas, where a significant variability appears at the heights 0–55 km. There is also a tendency for the intensity of year-to-year variations to decrease in comparison with day-to-day variations. In cold and warm periods the amplitude of perturbation waves with m = 2 both for day-to-day and year-to-year variations is greater than for waves with m = 1. Transient height areas in the interval of 20–30 km are more distinct for day-to-day variations of polar area.     

First laser measurements to space debris in Poland

The Borowiec Satellite Laser Ranging station (BORL 7811, Borowiec) being a part of the Space Research Centre of the Polish Academy of Sciences (SRC PAS) went through modernization in 2014–2015. One of the main tasks of the modernization was the installation of a high-energy laser module dedicated to space debris tracking. Surelite III by Continuum is a Nd:YAG pulse laser with 10?Hz repetition rate, a pulse width of 3–5?ns and a pulse energy of 450?mJ for green (532?nm). This new laser unit was integrated with the SLR system at Borowiec performing standard satellite tracking. In 2016 BORL 7811 participated actively to the observational campaigns related to the space debris targets from LEO region managed by the Space Debris Study Group (SDSG) of the International Laser Ranging Service (ILRS).Currently, Borowiec station regularly tracks 36 space debris from the LEO regime, including typical rocket bodies (Russian/Chinese) and cooperative targets like the inactive TOPEX/Poseidon, ENVISAT, OICETS and others. In this paper the first results of space debris laser measurements obtained by the Borowiec station in period August 2016 – January 2017 are presented. The results gained by the SRC PAS Borowiec station confirm the rotation of the defunct TOPEX/Poseidon satellite which spins with a period of approximately 10?s. The novelty of this work is the presentation of the sample results of the Chinese CZ-2C R/B target (NORAD catalogue number 31114) which is equipped (probably) with retroreflectors. Laser measurements to space debris is a very desirable topic for the next years, especially in the context of the Space Surveillance and Tracking (SST) activity. Some targets are very easy to track like defunct ENVISAT or TOPEX/Poseidon. On the other hand, there is a big population of different LEO targets with different orbital and physical parameters, which are challenging for laser ranging like small irregular debris and rocket boosters.     

Design and performances of laser retro-reflector arrays for Beidou navigation satellites and SLR observations

Beidou is the regional satellite navigation system in China, consisting of three kinds of orbiting satellites, MEO, GEO and IGSO, with the orbital altitudes of 21500–36000 km. For improving the accuracy of satellites orbit determination, calibrating microwave measuring techniques and providing better navigation service, all Beidou satellites are equipped with laser retro-reflector arrays (LRAs) to implement high precision laser ranging. The paper presents the design of LRAs for Beidou navigation satellites and the method of inclined installation of LRAs for GEO satellites to increase the effective reflective areas for the regional ground stations. By using the SLR system, the observations for Beidou satellites demonstrated a precision of centimeters. The performances of these LRAs on Beidou satellites are very excellent.     

Lakshita – Mining and research hub at L5

In this paper, the design of an orbital space settlement named Lakshita located at L5 for 10,000 residents having area of 1 × 10⁶ m² has been proposed, with the aim of fulfilling mining activities and space research in micro – g. All calculations are made in the perspective of a dynamic demography which could lead to the doubling of the population in next 25 years with initial population of 4500. The settlement consists of one residential torus, one agricultural torus, industrial cylinder and two docking cylinders rotating coaxially at 1 rpm. 2.3% of the total volume of settlement is provided for two docking cylinders with 6 docking ports enabling the elastic flow of space traffic, thereby providing continuous loading and unloading of cargo and passengers. Four pressurized sliding cylinders with 5.7 × 10⁵ m³ volume above the down surface area moving along the spokes fulfill the need of adaptation of visitors at half the gravity level of primary settlement volumes, as well provide wobble control. 1.1 × 10⁵ torr of pressure is provided above the down surface area of the residential torus. The power generation of 400 Mw, required for the functional need of Lakshita, will be obtained through SPS located at L4. The 14 h day and 10 h night cycle will be maintained by four mirrors attached on either side from the central cylinder. The walls of the settlement will be made up of three consecutive layers of super adobe, Nextel and Kevler-49 respectively to provide radiation and debris protection. An assortment of various facilities like appropriate distribution and management of water through an intended network of pipelines, accurate management of waste within the settlement has been provided.     

Photon counting detector for space debris laser tracking and lunar laser ranging

We are reporting on a design, construction and performance of solid state photon counting detector package which has been designed for laser tracking of space debris. The detector has been optimized for top photon detection efficiency and detection delay stability. The active area of the commercially available avalanche photodiode manufactured on Si (SAP500 supplied by Laser Components, Inc.) is circular with a diameter of 500 μm. The newly designed control circuit enables to operate the detection sensor at a broad range of biases 5–50 V above its breakdown voltage of 125 V. This permits to select a right trade-off between photon detection efficiency, timing resolution and dark count rate. The photon detection efficiency exceeds 70% at the wavelength of 532 nm. This is the highest photon detection efficiency ever reported for such a device. The timing properties of the detector have been investigated in detail. The timing resolution is better than 80 ps r.m.s, the detection delay is stable within units of picoseconds over several hours of operation. The detection delay stability in a sense of time deviation of 800 fs has been achieved. The temperature change of the detection delay is 0.5 ps/K. The detector has been tested as an echo signal detector in laser tracking of space debris at the satellite laser station in Graz, Austria. Its application in lunar laser ranging is under consideration by several laser stations.     

Cowpeas and pinto beans: Performance and yields of candidate space crops in the laboratory biosphere closed ecological system

An experiment utilizing cowpeas (Vigna unguiculata L.), pinto beans (Phaseolus vulgaris L.) and Apogee ultra-dwarf wheat (Triticum sativa L.) was conducted in the soil-based closed ecological facility, Laboratory Biosphere, from February to May 2005. The lighting regime was 13 h light/11 h dark at a light intensity of 960 μmol m⁻² s⁻¹, 45 mol m⁻² day⁻¹ supplied by high-pressure sodium lamps. The pinto beans and cowpeas were grown at two different planting densities. Pinto bean production was 341.5 g dry seed m⁻² (5.42 g m⁻² day⁻¹) and 579.5 dry seed m⁻² (9.20 g m⁻² day⁻¹) at planted densities of 32.5 plants m⁻² and 37.5 plants m⁻², respectively. Cowpea yielded 187.9 g dry seed m⁻² (2.21 g m⁻² day⁻¹) and 348.8 dry seed m⁻² (4.10 g m⁻² day⁻¹) at planted densities of 20.8 plants m⁻² and 27.7 plants m⁻², respectively. The crop was grown at elevated atmospheric carbon dioxide levels, with levels ranging from 300–3000 ppm daily during the majority of the crop cycle. During early stages (first 10 days) of the crop, CO₂ was allowed to rise to 7860 ppm while soil respiration dominated, and then was brought down by plant photosynthesis. CO₂ was injected 27 times during days 29–71 to replenish CO₂ used by the crop during photosynthesis. Temperature regime was 24–28 °C day/deg 20–24 °C night. Pinto bean matured and was harvested 20 days earlier than is typical for this variety, while the cowpea, which had trouble establishing, took 25 days more for harvest than typical for this variety. Productivity and atmospheric dynamic results of these studies contribute toward the design of an envisioned ground-based test bed prototype Mars base.     

Chlorophyll,calcite, and suspended sediment concentrations in the Bay of Bengal and the Arabian Sea at the river mouths

Chlorophyll and suspended sediment concentrations (SSC) and sea surface temperature (SST) are important parameters in assessing the productivity of coastal regions. Numerous rivers flow into the eastern (Ganga, Subernarekha, Mahanadi, Godavari, Krishna, Penner, and Kaveri) and western (Narmada, Tapti, and Indus) coasts of the Indian sub-continent. Using IRS P4 (Oceansat-1) Ocean Color Monitor (OCM) and Moderate Resolution Imaging Spectroradiometer (MODIS) data, we have retrieved chlorophyll, calcite, and SSC near the mouth of these rivers for the period during 2000–2004. The maxima of chlorophyll-a concentrations at the river mouth is much higher for the Himalayan and north India rivers (Ganga, Subernarekha, Mahanadi, and Indus) (10–14 mg/m³) compared to rivers in the southern parts of India (Kaveri and Penner) (∼4 mg/m³). The maxima of calcite concentration (∼45 moles/m³), chlorophyll (∼14 mg/m³), and sediment concentrations (∼9 g/m³) near river mouth are found to be influenced by river discharges (Ganga and Brahmaputra) during the monsoon season. The calcite concentration (∼45 moles/m³) at the mouth of Ganga river shows a major peak with the onset of monsoon season (June–July) followed by a maxima in chlorophyll-a with a time lag of 1–2 months. The Krishna, Kaveri, and Penner rivers show low chlorophyll concentrations (3–8 mg/m³), high calcite (0–40 moles/m³), and low SSC (<3 g/m³) compared to Narmada and Tapti rivers (chlorophyll-a 12–14 mg/m³, calcite 0–2 moles/m³, and SSC 13–19 g/m³). The Indus river shows similar behavior (maxima of chlorophyll ∼13 mg/m³ and SSC ∼8 g/m³) with respect to Ganga river except for high calcite concentration during winter months (∼25 moles/m³). The characteristics of the chlorophyll, calcite, and SSC at the mouth of these rivers show spatial and temporal variability along the eastern and westerns coasts of India which are found to differ widely. A comparison of the chlorophyll concentrations using OCM and MODIS data shows low chlorophyll concentrations in the Bay of Bengal as compared to the Arabian Sea.     

The water cycle in closed ecological systems: Perspectives from the Biosphere 2 and Laboratory Biosphere systems

To achieve sustainable, healthy closed ecological systems requires solutions to challenges of closing the water cycle – recycling wastewater/irrigation water/soil medium leachate and evaporated water and supplying water of required quality as needed for different needs within the facility. Engineering Biosphere 2, the first multi-biome closed ecological system within a total airtight footprint of 12,700 m² with a combined volume of 200,000 m³ with a total water capacity of some 6 × 10⁶ L of water was especially challenging because it included human inhabitants, their agricultural and technical systems, as well as five analogue ecosystems ranging from rainforest to desert, freshwater ecologies to saltwater systems like mangrove and mini-ocean coral reef ecosystems. By contrast, the Laboratory Biosphere – a small (40 m³ volume) soil-based plant growth facility with a footprint of 15 m² – is a very simplified system, but with similar challenges re salinity management and provision of water quality suitable for plant growth. In Biosphere 2, water needs included supplying potable water for people and domestic animals, irrigation water for a wide variety of food crops, and recycling and recovering soil nutrients from wastewater. In the wilderness biomes, providing adequately low salinity freshwater terrestrial ecosystems and maintaining appropriate salinity and pH in aquatic/marine ecosystems were challenges. The largest reservoirs in Biosphere 2 were the ocean/marsh with some 4 × 10⁶ L, soil with 1 to 2 × 10⁶ l, primary storage tank with 0 to 8 × 10⁵ L and storage tanks for condensate and soil leachate collection and mixing tanks with a capacity of 1.6 × 10⁵ L to supply irrigation for farm and wilderness ecosystems. Other reservoirs were far smaller – humidity in the atmosphere (2 × 10³ L), streams in the rainforest and savannah, and seasonal pools in the desert were orders of magnitude smaller (8 × 10⁴ L). Key technologies included condensation from humidity in the air handlers and from the glass space frame to produce high quality freshwater, wastewater treatment with constructed wetlands and desalination through reverse osmosis and flash evaporation were key to recycling water with appropriate quality throughout the Biosphere 2 facility. Wastewater from all human uses and the domestic animals in Biosphere 2 was treated and recycled through a series of constructed wetlands, which had hydraulic loading of 0.9–1.1 m³ day⁻¹ (240–290 gal d⁻¹). Plant production in the wetland treatment system produced 1210 kg dry weight of emergent and floating aquatic plant wetland which was used as fodder for the domestic animals while remaining nutrients/water was reused as part of the agricultural irrigation supply. There were pools of water with recycling times of days to weeks and others with far longer cycling times within Biosphere 2. By contrast, the Laboratory Biosphere with a total water reservoir of less than 500 L has far quicker cycling rapidity: for example, atmospheric residence time for water vapor was 5–20 min in the Laboratory Biosphere vs. 1–4 h in Biosphere 2, as compared with 9 days in the Earth’s biosphere. Just as in Biosphere 2, humidity in the Laboratory Biosphere amounts to a very small reservoir of water. The amount of water passing through the air in the course of a 12-h operational day is two orders of magnitude greater than the amount stored in the air. Thus, evaporation and condensation collection are vital parts of the recycle system just as in Biosphere 2. The water cycle and sustainable water recycling in closed ecological systems presents problems requiring further research – such as how to control buildup of salinity in materially closed ecosystems and effective ways to retain nutrients in optimal quantity and useable form for plant growth. These issues are common to all closed ecological systems of whatever size, including planet Earth’s biosphere and are relevant to a global environment facing increasing water shortages while maintaining water quality for human and ecosystem health. Modular biospheres offer a test bed where technical methods of resolving these problems can be tested for feasibility.     

A high-performance ground-based prototype of horn-type sequential vegetable production facility for life support system in space

Vegetable cultivation plays a crucial role in dietary supplements and psychosocial benefits of the crew during manned space flight. Here we developed a ground-based prototype of horn-type sequential vegetable production facility, named Horn-type Producer (HTP), which was capable of simulating the microgravity effect and the continuous cultivation of leaf–vegetables on root modules. The growth chamber of the facility had a volume of 0.12 m³, characterized by a three-stage space expansion with plant growth. The planting surface of 0.154 m² was comprised of six ring-shaped root modules with a fibrous ion-exchange resin substrate. Root modules were fastened to a central porous tube supplying water, and moved forward with plant growth. The total illuminated crop area of 0.567 m² was provided by a combination of red and white light emitting diodes on the internal surfaces. In tests with a 24-h photoperiod, the productivity of the HTP at 0.3 kW for lettuce achieved 254.3 g eatable biomass per week. Long-term operation of the HTP did not alter vegetable nutrition composition to any great extent. Furthermore, the efficiency of the HTP, based on the Q-criterion, was 7 × 10⁻⁴ g² m⁻³ J⁻¹. These results show that the HTP exhibited high productivity, stable quality, and good efficiency in the process of planting lettuce, indicative of an interesting design for space vegetable production.     

Vertical wavenumber spectra of atmospheric ozone measured from ozonesonde observations

Vertical profiles of ozone have been measured at balloon altitudes. Our purpose is to examine the character of vertical wavenumber spectra of ozone fluctuations, to assess the possible roles of gravity wave field in ozone fluctuations, and to determine dominant vertical wavelengths of ozone spectra. Vertical wavenumber spectra of 12 ozone fluctuations obtained during June–August 2003 are presented. Results indicate that mean spectral slopes in the wavenumber range from 4.69 × 10⁻⁴ to 2.50 × 10⁻³ cyc/m are about −2.91 in the troposphere and −2.87 in the lower stratosphere, which is close to the slope of −3 predicted by current gravity wave saturation models. The consistency of the observed spectral slopes with the value of −3 predicted by current gravity wave saturation models suggests that the observed ozone fluctuations are due primarily to atmospheric gravity waves. At m = 1/(1000 m) the mean spectral amplitude is over 30 times larger in the lower stratosphere than in the troposphere. Mean vertical wavenumber spectra in area-preserving form reveal dominant vertical wavelengths of ∼2.6 km in the troposphere and ∼2.7 km in the lower stratosphere, which is consistent with the values varying between 1.5 and 3.0 km estimated from the velocity field and temperature field at these heights.     

Dynamical evolution of high area-to-mass ratio debris released into GPS orbits

A large set of simulations, including all the relevant perturbations, was carried out to investigate the long-term dynamical evolution of fictitious high area-to-mass ratio (A/M) objects released, with a negligible velocity variation, in each of the six orbital planes used by Global Positioning System (GPS) satellites. As with similar objects discovered in near synchronous trajectories, long lifetime orbits, with mean motions of about 2 revolutions per day, were found possible for debris characterized by extremely high area-to-mass ratios. Often the lifetime exceeds 100 years up to A/M ∼ 45 m²/kg, decreasing rapidly to a few months above such a threshold. However, the details of the evolution, which are conditioned by the complex interplay of solar radiation pressure and geopotential plus luni-solar resonances, depend on the initial conditions. Different behaviors are thus possible. In any case, objects like those discovered in synchronous orbits, with A/M as high as 20–40 m²/kg, could also survive in this orbital regime, with semi-major axes close to the semi-synchronous values, with maximum eccentricities between 0.3 and 0.7, and with significant orbit pole precessions (faster and wider for increasing values of A/M), leading to inclinations between 30° and more than 90°.