DISCOS shapes

DISCOS is ESA’s database of objects in space. For many objects it gives a shape label and dimensions. LightCurve turns them into a 3D model.

The 20 shapes

These are the 20 most frequent shape labels of a 73,392-object DISCOS extract (38,266 objects have a shape; 405 distinct labels). Number of objects in brackets.

Shape	Objects	Shape	Objects
Box + 2 Pan	9,612	Cyl + Cone	322
Cyl	8,805	Irr	315
Box + 1 Pan	5,407	Box + 2 Ant	216
Box	2,716	Sphere + Cone	199
Sphere	1,587	Hex Poly + 2 Pan	196
Cone	1,154	Trunc Cone	184
Cyl + 1 Nozzle	799	Cyl + Sphere + 2 Pan	182
Cyl + 2 Pan	781	Sphere + Cyl + 1 DCone	173
Trap Box + 2 Pan	759	Cyl + 1 Ant	169
Sphere + Cyl	758	Cyl + 6 Pan	166

Enter the dimensions

Pick DISCOS shape (ESA)

In the Model section of the Satellite tab. The shape starts with typical DISCOS dimensions: the median of the objects with that shape (for the box shapes, leaving out the flat buses of mega-constellations such as Starlink and OneWeb, so that the default is a representative box).

Choose the shape

The fields change with the shape: width, height and depth for box-like bodies; diameter and height for bodies of revolution; span when the object has appendages.

Enter the cross-sections

Maximum, minimum and mean cross-sections (m²). The maximum is used to derive the width of the solar arrays.

Check the result

The panel shows the resolved body and arrays, the model’s cross-sections next to the DISCOS ones, and the assumptions made.

What is derived

DISCOS does not describe the appendages in detail. LightCurve fills the gaps and lists each assumption under the shape:

Quantity	Rule
Array length	(span − body extent along the array axis) / arrays per side
Array width	(largest cross-section − largest body face) / (array count × length); the body height when the cross-section is unknown; adjustable
Missing box dimension	The largest known one
Composite bodies	The share of the cone or second part (default 0.3) and the taper of cones and trapezoids are adjustable
Irregular	A random convex polyhedron inside the width × height × depth box, the same for the same object

Frame: box width along Y, depth along X, height along Z (toward the Earth); bodies of revolution along X; arrays along ±Y and Sun-tracking. If the width is the smallest box dimension, width and depth are swapped, so that the arrays extend along one of the two larger dimensions.

Check against DISCOS

The panel compares the model’s cross-sections with the DISCOS ones, using the DISCOS definitions:

Body	Largest cross-section	Smallest cross-section
With arrays	Face-on view: largest body face (or side of the body of revolution) plus all the arrays, lying in the plane of that face	Edge-on view: smallest body face, arrays seen by their edge
Without arrays	True maximum, seen obliquely: √(A₁² + A₂² + A₃²) for a box	Smallest face

The arrays are modelled nearly without thickness, as DISCOS counts them. On about 2,000 objects of the extract, the model is within 5 % of DISCOS for:

Shape	Largest	Smallest
Box + 2 Pan	91 %	92 %
Cyl + 2 Pan	97 %	78 %
Box + 1 Pan	100 %	28 %
Trap Box + 2 Pan	99 %	1 %
Hex Poly + 2 Pan	65 %	65 %

Remaining differences: some DISCOS entries are inconsistent (largest cross-section smaller than a body face), and for “Box + 1 Pan” and “Trap Box + 2 Pan” DISCOS adds a term to the smallest cross-section that the dimensions do not explain. The mean cross-section follows a DISCOS convention that is not documented; the model’s mean is over all directions.

Import from a DISCOS export

Load a CSV export of DISCOS metadata (columns shape, width, height, depth, diameter, span, xSectMax, xSectMin, xSectAvg, plus identifiers), then search an object by NORAD number, COSPAR id or name. A click fills the shape and the dimensions. Shapes outside the 20 are mapped to the closest one and marked. See DISCOS export.

The export stays in memory for the session: it is not stored in the browser nor in the shared link.