Aerospace and Electronic Systems Magazine February 2018 - 44

Remote Sensing Satellites Conceptual Design
To identify the relevant parameters, PCA method can also be
used here. At this stage, also the curve fitting methods will be used to
determine the relation between the correlated parameters. Then, the
independent parameters will be maintained and the dependent ones
will be deleted. This process of pairwise comparison, maintaining and
removal of DPs, should continue until to remain one DP in each category. These three parameters which have the greatest impact on satellite performance are called the main parameters of satellite design.
By implementing this step, the performance MDPs of the cubesat passive optical payload will be as follows:
C

Orbit altitude (H)

Focal length (f)

Effective entrance aperture (D)

Step 7. Redefining the PPs based on the MDPs, determination
of DDs, and design space dimensionality reduction.
In this step, the formulas which define the quantitative criteria of
PRs (PPs) must be rewritten in terms of DPs. During rewriting the
formulas, the dependent DPs are replaced with the MDPs including E, M, and I. There are PPs and MDPs in the resulting formulas.
To create the design plane, the three MDPs including a parameter of Information, a parameter of Energy, and a parameter of
Matter must be combined in such a way that their number reduces
to two parameters. These binary combinations for example could
be displayed as (E/M, I/E) or (E/M, I/M) and they will be called design drivers (DDs). The DDs are better to provide physical insight
rather than to be just a parametric combination of MDPs. In order
to identify the best binary combinations of the MDPs, it is better to
focus on formulas which two of three MDPs are appeared in them.
The reference equations must be rewritten in terms of the DDs.
One of the DDs should be considered as function or dependent
variable and the other should be considered as independent variable. The reference equations should be rearranged in such a way
that the dependent variable is moved to the left and the independent variables are moved to the right side of the equation:

According to the Table 7, the following binary combinations of
the performance MDPs of the cubesat optical payload could be
created:
 f H
M E 
 I , M   first :  D , f 




or
M M 
 f f 
 ,   second :  , 
 I E 
D H

According to the definition of each of these parameters [27],
they could be categorized as depicted in the Table 7.

 E 
M

 M  = f1  I , P1 
  P1


 E 
M

*
 M  = f 2  I , P2 
  P2



W M W M
M M 
≡
 , 
, ≡
S
I P
E
 I E 

(4)

An optical system can be described by its so-called infinity
F-number or F-stop, often written as f/, F, F No., or F#. It is defined as f/D, where D is the effective entrance aperture, which is
the effective diameter of the lens or primary telescope mirror. The
magnification (M) or scale, f/H, is the ratio of the image size to the
object size [1]. Since the f/H and f/D are two physical concepts,
these two ratios will be selected as initial DDs.

Step 8. Creating a variety of plane designs and selecting the best.
In this step, a variety of design planes must be drawn using DDs,
which were obtained in the previous step. Those samples, which
were excluded in the first step for rechecking the results, should
be used in this step. In this step, using the new statistical samples,
the design plane which mostly matches the reality will be selected.
The performance sizing of the cubesat passive optical payload
has been fulfilled based on the requirements and constraints which
govern its performance using the stepwise method presented in the
following:
1. Sizing to the Spatial Resolution Requirements.
The spatial resolution requirements can be summarized in the following inequality:

Equation (6) shows a relation between DD, f/H, and the PP, GSD,
where x is the detector element size or the sensor pixel size.
f
x
=
H GSD

(6)

Table 7.

...

Categorization of the Performance MDPs of the
Cubesat Optical Payload

 E 
M

 M  = f n  I , Pn 
  Pn



Based on the airplane sizing method, the following binary
combinations could be written:

Parameter

W M T
E
M E 
≡
, ≡
 , 
S
I W M
 I M
or

(5)

GSD ≤ 30 m

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Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine February 2018