IEEE Geoscience and Remote Sensing Magazine - June 2015 - 21

Cum. Duty [%]

5 acquisitions per bistatic cycle. This can be
tAble 3. siMplified high-level scheduling during bistAtic phAses.
obtained scheduling acquisitions every other
cycle (32 days) or, every three cycles (48 days).
ApplicAtion
Ascending
descending
MAxiMuM frequency
The acquisitions are grouped by latitude, reForest + "Global" Bistatic, quad pol,
Every 2-3 cycles
flecting the latitude dependence of the effec80 MHz, 175 km (B4)
tive baselines. Forest and other acquisitions
Agriculture
Monostatic, quad pol, Every cycle
requiring quad-pol modes use a 175 km swath
80 MHz, 175 km (B4)
mode, while applications requiring only single
Deformation
Monostatic, single pol, Monostatic, single
Every cycle
80 MHz, 175 km (B1)
pol, 25 MHz, 350 km
or dual-pol acquisitions benefit from wider,
Ice sheets
Monostatic, quad pol, 8 cycles/year
350 km, swath modes. This doubles the num80 MHz, 175 km (B4)
ber of potential acquisitions and, consequentShip routing
Monostatic, dual pol, 80 MHz, 350 km (B2)
Every cycle
ly, relaxes the scheduling.
Wind speed/
Monostatic, dual pol, 25 MHz, 350 km, 50 m Every opportunity
Table 3 provides a very high level and simocean monitoring
plified overview of the basic observation scenario foreseen during a bistatic phase. Here,
different applications have been grouped, exploiting obser◗ extensive data processing for the provision of highly agvation synergies between them. For example, forest acquigregated information products
sitions are partially covered by the acquisitions required to
While each of these innovations may justify a new satelprovide the global reference maps. The table also hints at the
lite mission by itself, their combination makes Tandem-L
acquisition timeline optimization that can be achieved by
a more than unique mission that has the potential to inidistributing the observation requirements between ascendtiate a new era in the geosciences. The integration of the
ing and descending passes. Figure 15 shows how this schedulTandem-L data products in ecological, environmental and
ing translates into daily duty-cycles, segregated by operating
geophysical models will moreover enable a new global
modes. The baseline timeline drives the number of bistatic
view of the Earth system and its dynamics, triggering a
quad-pol (B4) acquisitions, while seasons can be recognized
performance leap in ecosystem, climate change and solid
in the acquisition timeline for agriculture related (monostatic
Earth modelling. In this sense, Tandem-L has the potential
B4) and ice related modes. In contrast, modes associated to
to change the way ecosystem dynamics and geo-hazards
the geosphere (deformations) show an almost constant proare addressed today.
file (with variations obeying to acquisition conflicts).
The scientific importance and uniqueness of Tandem-L
can also be assessed by comparing the spectrum and quality
VI. CONCLUSIONS AND OUTLOOK
of the Tandem-L information products with those available
This paper provides an overview of the Tandem-L mission
today or aimed at by future remote sensing missions. Table
including the science requirements, mission concept, obser4 illustrates the uniqueness of Tandem-L in the context of
vation scenario and instrument design. Beside the scientific
some exemplary applications and products. Note that this
component, the distinguishing feature of Tandem-L is the
list is by no means meant to be complete and exhaustive.
high degree of innovation with respect
to the methodology and technology.
Examples are polarimetric SAR interDaily Duty Cycle (Cumulative)
ferometry for measuring forest height,
50
A1
multiple-pass coherence tomography for
B1
determining the vertical structure of veg40
B4 (Bist)
etation and ice, utilization of the latest
B4
E2
beamforming techniques for increasing
30
A2
the swath width and imaging resolution
and close formation flying of two coop20
erative radar satellites with adjustable
spacing. Tandem-L is characterized by
10
three major innovations:
◗ systematic global data acquisition
0
0
50
100
150
200
250
300
350
with unprecedented spatial and temTime [Day]
poral resolution using novel SAR imaging modes
◗ formation flight of two radar satelFIgUre 15. Daily duty cycles segregated by observation mode during one year of
lites with variable cross-track basebistatic observations. Imaging modes B1 and B4 are described in Table 2. Imaging modes
lines for single-pass interferometry
A1/A2 are similar to B1/B2, but with 20+5 MHz split bandwidth. Mode E2 is a dual-pol
and tomography
imaging mode with 20 MHz bandwidth and 50 m azimuth resolution.
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Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - June 2015