The James Webb Space Telescope Mission: Optical Telescope Element Design, Development, and Performance

The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the Universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5-layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wavefront sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.Comment: accepted by PASP for JWST Overview Special Issue; 34 pages, 25 figure

Public Policies and Private Savings and Investment in Sub-Saharan Africa

This paper assesses empirically the role of public policies in stimulating private savings and investment in sub-Saharan African countries, based on data for the period 1986-92. The main findings of the analysis are as follows: (i) policies effective in stimulating private savings and investment include those that keep the rate of inflation low, reduce macroeconomic uncertainty, promote financial deepening, and lower the external debt burden; (ii) measures that promote structural reforms and reduce the budget deficit (without lowering government investment) help to raise private investment; and (iii) declines in government savings are only partially offset by increases in private savings.

Growth in Sub-Saharan Africa

The paper investigates empirically the determinants of per capita economic growth for a large sample of sub-Saharan African countries during 1981-92. The results indicate that (1) an increase in private investment has a relatively large positive impact on per capita growth; (2) growth is stimulated by public policies that lower the budget deficit in relation to GDP (without reducing government investment), reduce the rate of inflation, maintain external competitiveness, promote structural reforms, encourage human capital development, and slow population growth; and (3) per capita income converges after controlling for human capital development and public policies.

Growth in Sub-Saharan Africa

The paper investigates empirically the determinants of economic growth for a large sample of sub-Saharan African countries during 1981-92. The results indicate that (i) an increase in private investment has a relatively large positive impact on per capita growth; (ii) growth is stimulated by public policies that lower the budget deficit in relation to GDP (without reducing government investment), reduce the rate of inflation, maintain external competitiveness, promote structural reforms, encourage human capital development, and slow population growth; and (iii) convergence of per capita income occurs after controlling for human capital development and public policies.

The Gambia

The Gambia, one of the least developed countries in Africa, has been pursuing corrective economic policies since 1985, aimed at restroing financial stability and laying the basis for strong and sustainable economic growth. Supported by IMF policy advice and financing. The Gambia's economic performance has improved considerably since 1985. This study discusses Gambian adjustment policies and their benefits.

Adjustment for Growth

Over the past two decades, sub-Saharan Africa has lagged behind other regions in economic performance. The important overall indicators of performance, however, mask wide differences among countries. On the whole, countries that effectively implemented comprehensive adjustment and reform programs showed better results. Their experiences demonstrate that an expansion in private saving and investment is key to achieving gains in real per capita GDP. The four papers included in this publication provide a cross country analysis that assesses empirically the role of publlic policies in stimulating private saving and investment in the region in 1986-92 and describe the adjustment experiences of Ghana (1983-91), Senegal (1978-1993), and Uganda (1987-94).

Effects of Macroeconomic Stabilityon Growth, Savings, and Investment in Sub-Saharan Africa

The analysis of this paper indicates that the unsatisfactory overall economic performance of sub-Saharan African countries during 1986–93 was due to inappropriate policies pursued by a number of countries. The countries that have pursued broadly appropriate adjustment policies have performed much better, achieving positive per capita GDP growth. The analysis is supported with an econometric investigation of the effects of macroeconomic policies, structural reforms, and exogenous factors on economic performance. The results indicate that progress in achieving macroeconomic stability and implementing structural reforms have been conducive to better growth, savings, and private investment.

Sub-Saharan Africa

This paper assesses the economic performance during 1986-93 of sub-Saharan African countries as a group and of selected analytical subgroups of countries.

Ghana

The first sub-Saharan African country to pursue broad economic and structural reform - aided by external finance and technical aid - Ghana is an example of adjustment with growth. Ghana's experience, discussed in this paper, illustrates the need for complementary policy actions and the right sequencing and speed of reforms.