Instrument
 
Grids
 
Fine grids are being fabricated using new, innovative technology for Fourier-transform imaging in X-rays and gamma rays. The square grids are manufactured by Van Beek Consultancy, the round grids by Tecomet. The grid mounts are manufactured by Goddard Space Flight Center. Optical and x-ray tests were performed by Goddard Space Flight Center.
 
 
 

Grid Layout

 
 
HESSI Grid Specifications - Nominal (as of 6/24/99)
Grid #

1

2

3

4

Nominal FWHM Resolution (arcsec)

2.26

3.92

6.79

11.8

Angular Pitch (arcsec)

4.52

7.84

13.57

23.5

Pitch (mm)

0.034

0.059

0.102

0.177

Source

Tecomet

Tecomet

Tecomet

Tecomet

Slit (mm)

0.020

0.035

0.061

0.106

Slat (mm)

0.014

0.024

0.041

0.071

Maximum Fractional Transmission

0.60

0.60

0.60

0.60

Total Grid Thickness (mm)

1.2

2.1

3.6

6.2

Field of View (degrees)

1.0

1.0

1.0

1.0

Shape

Round

Round

Round

Round

Mount Material

Titanium

Titanium

Titanium

Titanium

High-Z Absorber

Molybdenum

Tungsten

Tungsten

Tungsten

High-Z Absorber Density (g mm-3)

0.0102

0.0180

0.0180

0.0180

High-Z Absorber Layer Thickness (mm)

0.018

0.025

0.0508

0.0762

Epoxy Thickness (per layer)

0.0026

0.0026

0.0026

0.0026

Nominal Layer Count

58

76

67

79

Diameter (mm)

90

90

90

90

Outer Diameter (mm)

110

110

110

110

Rim Width (mm)

10

10

10

10

Rim (+ring) Material

Moly+Kovar

Tungsten+Kovar

Tungsten

Tungsten

Rim (+ring) Height

1.2+4.0

2.1+3.0

3.6

6.2

Mass (g) (incl. ring estimate)

173

288

379

626

Grid #

5

6

7

8

9

Nominal FWHM Resolution (arcsec)

20.4

35.3

61.1

105.8

183.2

Angular Pitch (arcsec)

40.7

70.5

122.2

211.6

366.5

Pitch (mm)

0.306

0.530

0.918

1.590

2.754

Source

VBC

VBC

VBC

VBC

VBC

Slit (mm)

0.184

0.318

0.477

0.811

1.487

Slat (mm)

0.122

0.212

0.441

0.779

1.267

Maximum Fractional Transmission

0.60

0.60

0.52

0.51

0.54

Total Grid Thickness (mm)

10.7

18.6

6.2

6.2

30.0

Field of View (degrees)

1.0

1.0

4.4

7.5

2.8

Shape

Square

Square

Square

Square

Square

Mount Material

Aluminum

Aluminum

Aluminum

Aluminum

Aluminum

High-Z Absorber

Tungsten

Tungsten

Tungsten

Tungsten

Tungsten

High-Z Absorber Density (g mm-3)

0.0190

0.0190

0.0185

0.0190

0.0190

High-Z Absorber Layer Thickness (mm)

10.7

18.6

6.2

6.2

30.0

Epoxy Thickness (per layer)

 

 

 

 

 

Nominal Layer Count

1

1

1

1

1

Diameter (mm)

90

90

90

90

90

Outer Diameter (mm)

110

110

110

110

110

Rim Width (mm)

10

10

10

10

10

Rim (+ring) Material

Aluminum

Aluminum

Aluminum

Aluminum

Aluminum

Rim (+ring) Height

20.7

28.6

16.2

16.2

40.0

Mass (g) (incl. ring estimate)

1031

1517

681

706

2672